Sidebar-Kompaktmodus polieren, Dashboard-Kalender ergänzen

- MainWindow: App-Titel durch ein kompaktes Logo-Badge ersetzt; im
  minimierten Zustand der Sidebar werden Nav-Icons automatisch größer
  und zentriert, Beschriftungen sowie Abschnittsüberschriften blenden
  aus (Classes-Binding auf DrawerPage.IsOpen).
- LearningGroup.IsOwnClass: neues Feld, per Checkbox im Gruppen-Dialog
  editierbar ("Gehört zu meiner Klasse"), mehrere Gruppen markierbar.
- Dashboard: kleiner Monatskalender mit Monatsnavigation, dezenter
  Einfärbung für Unterrichtstage, Klausur-Marker und Rahmen-Hervor-
  hebung für Tage der eigenen Klasse, inkl. Tooltip und Legende.
  Feste Kartenposition/-breite, damit weder Monatsnamenlänge noch die
  wachsende Lerngruppen-Liste das Layout verschieben.
- TODO.md: geplante Kalender-Detailansicht (Tag auswählen → Termine
  des Tages mit Sprung in die jeweilige Ansicht) unter 9.8 vermerkt.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

LehrerApp.Desktop/Views/Dashboard/DashboardView.axaml

@@ -13,7 +13,7 @@
         <TextBlock Text="{Binding CurrentDate}" FontSize="24" FontWeight="SemiBold"/>
       </StackPanel>
 
-      <Grid ColumnDefinitions="*,*" RowDefinitions="Auto,Auto">
+      <Grid ColumnDefinitions="*,*" RowDefinitions="Auto,Auto,Auto">
 
         <!-- Heutige Stunden -->
         <Border Grid.Column="0" Grid.Row="0" Margin="0,0,8,8"
@@ -67,8 +67,108 @@
           </StackPanel>
         </Border>
 
-        <!-- Meine Lerngruppen -->
-        <Border Grid.Column="0" Grid.Row="1" Grid.ColumnSpan="2"
+        <!-- Kalender: feste Position direkt unter Heute/Aufgaben, damit die wachsende
+             Lerngruppen-Liste darunter ihn nicht nach unten verdrängt. -->
+        <Border Grid.Column="0" Grid.Row="1" Margin="0,0,8,8" HorizontalAlignment="Left"
+                Background="{DynamicResource SystemControlBackgroundAltHighBrush}"
+                CornerRadius="8" Padding="16">
+          <StackPanel Spacing="8">
+            <StackPanel.Styles>
+              <!-- Basiswerte als Style (nicht lokal), damit die spezifischeren Selektoren
+                   (z.B. .daycell.ownclass) sie überschreiben können. -->
+              <Style Selector="Border.daycell">
+                <Setter Property="Background" Value="Transparent"/>
+                <Setter Property="BorderThickness" Value="0"/>
+                <Setter Property="BorderBrush" Value="Transparent"/>
+                <Setter Property="Opacity" Value="1"/>
+              </Style>
+              <Style Selector="Border.daycell.haslesson">
+                <Setter Property="Background" Value="#14808080"/>
+              </Style>
+              <Style Selector="Border.daycell.ownclass">
+                <Setter Property="BorderThickness" Value="2"/>
+                <Setter Property="BorderBrush" Value="{DynamicResource SystemControlBackgroundAccentBrush}"/>
+              </Style>
+              <Style Selector="Border.daycell.outside">
+                <Setter Property="Opacity" Value="0.35"/>
+              </Style>
+              <Style Selector="TextBlock.daynum">
+                <Setter Property="FontWeight" Value="Normal"/>
+              </Style>
+              <Style Selector="TextBlock.daynum.today">
+                <Setter Property="FontWeight" Value="Bold"/>
+                <Setter Property="Foreground" Value="{DynamicResource SystemControlForegroundAccentBrush}"/>
+              </Style>
+            </StackPanel.Styles>
+
+            <Grid ColumnDefinitions="Auto,*,Auto,Auto,Auto">
+              <TextBlock Grid.Column="0" Text="KALENDER" FontSize="11" FontWeight="Bold"
+                         Opacity="0.5" VerticalAlignment="Center"/>
+              <TextBlock Grid.Column="1" Text="{Binding CalendarMonthLabel}" FontSize="13"
+                         FontWeight="SemiBold" TextAlignment="Center" VerticalAlignment="Center"
+                         Width="130" Margin="12,0"/>
+              <Button Grid.Column="2" Content="Heute" FontSize="11" Padding="8,2"
+                      Command="{Binding CalendarTodayCommand}" Margin="0,0,4,0"/>
+              <Button Grid.Column="3" Content="‹" Padding="8,2" Command="{Binding PrevMonthCommand}"/>
+              <Button Grid.Column="4" Content="›" Padding="8,2" Command="{Binding NextMonthCommand}" Margin="4,0,0,0"/>
+            </Grid>
+
+            <ItemsControl ItemsSource="{Binding CalendarWeekdayHeaders}">
+              <ItemsControl.ItemsPanel>
+                <ItemsPanelTemplate><UniformGrid Columns="7"/></ItemsPanelTemplate>
+              </ItemsControl.ItemsPanel>
+              <ItemsControl.ItemTemplate>
+                <DataTemplate>
+                  <TextBlock Text="{Binding}" FontSize="10" Opacity="0.5" FontWeight="Bold"
+                             HorizontalAlignment="Center" Width="32"/>
+                </DataTemplate>
+              </ItemsControl.ItemTemplate>
+            </ItemsControl>
+
+            <ItemsControl ItemsSource="{Binding CalendarDays}">
+              <ItemsControl.ItemsPanel>
+                <ItemsPanelTemplate><UniformGrid Columns="7"/></ItemsPanelTemplate>
+              </ItemsControl.ItemsPanel>
+              <ItemsControl.ItemTemplate>
+                <DataTemplate x:DataType="vm:CalendarDayCell">
+                  <Border Classes="daycell" Classes.ownclass="{Binding IsOwnClassDay}"
+                          Classes.haslesson="{Binding HasLesson}"
+                          Classes.outside="{Binding !IsCurrentMonth}"
+                          Width="32" Height="32" Margin="1" CornerRadius="6"
+                          ToolTip.Tip="{Binding Tooltip}">
+                    <Grid>
+                      <TextBlock Classes="daynum" Classes.today="{Binding IsToday}"
+                                 Text="{Binding DayNumber}" FontSize="12"
+                                 HorizontalAlignment="Center" VerticalAlignment="Center"/>
+                      <Ellipse Width="5" Height="5" Fill="#E53935" Margin="0,0,0,3"
+                               HorizontalAlignment="Center" VerticalAlignment="Bottom"
+                               IsVisible="{Binding HasExam}"/>
+                    </Grid>
+                  </Border>
+                </DataTemplate>
+              </ItemsControl.ItemTemplate>
+            </ItemsControl>
+
+            <StackPanel Orientation="Horizontal" Spacing="14" Margin="0,4,0,0">
+              <StackPanel Orientation="Horizontal" Spacing="4">
+                <Border Width="10" Height="10" CornerRadius="3" Background="#14808080"/>
+                <TextBlock Text="Unterricht" FontSize="10" Opacity="0.6"/>
+              </StackPanel>
+              <StackPanel Orientation="Horizontal" Spacing="4">
+                <Ellipse Width="7" Height="7" Fill="#E53935"/>
+                <TextBlock Text="Klausur" FontSize="10" Opacity="0.6"/>
+              </StackPanel>
+              <StackPanel Orientation="Horizontal" Spacing="4">
+                <Border Width="10" Height="10" CornerRadius="3" BorderThickness="2"
+                        BorderBrush="{DynamicResource SystemControlBackgroundAccentBrush}"/>
+                <TextBlock Text="Meine Klasse" FontSize="10" Opacity="0.6"/>
+              </StackPanel>
+            </StackPanel>
+          </StackPanel>
+        </Border>
+
+        <!-- Meine Lerngruppen: wächst mit der Zeit, deshalb ganz unten und volle Breite -->
+        <Border Grid.Column="0" Grid.Row="2" Grid.ColumnSpan="2"
                 Background="{DynamicResource SystemControlBackgroundAltHighBrush}"
                 CornerRadius="8" Padding="16">
           <StackPanel>

LehrerApp.Desktop/Views/Groups/AddGroupDialog.axaml

@@ -64,6 +64,9 @@
         </StackPanel>
       </Grid>
 
+      <CheckBox Content="Gehört zu meiner Klasse" IsChecked="{Binding IsOwnClass}"
+                ToolTip.Tip="Für die farbliche Hervorhebung im Dashboard-Kalender. Mehrere Gruppen (Klasse + zugehörige Kurse) können markiert werden."/>
+
       <TextBlock Text="{Binding ValidationMessage}" Foreground="Red" FontSize="12"
                  IsVisible="{Binding ValidationMessage, Converter={x:Static StringConverters.IsNotNullOrEmpty}}"/>
     </StackPanel>

LehrerApp.Desktop/Views/MainWindow.axaml

@@ -21,10 +21,10 @@
     darunter als Overlay-Drawer mit Hamburger-Button (automatisch).
     Kein eigener Code nötig.
   -->
-  <DrawerPage DrawerLength="220"
+  <DrawerPage x:Name="RootDrawer"
+              DrawerLength="220"
               DrawerBehavior="Auto"
               DrawerLayoutBehavior="CompactInline"
-              
               Content="{Binding CurrentPage}">
 
     <DrawerPage.DataTemplates>
@@ -52,15 +52,48 @@
     </DrawerPage.DataTemplates>
 
     <DrawerPage.Drawer>
-      <DockPanel>
+      <DockPanel Classes.compact="{Binding !#RootDrawer.IsOpen}">
+        <DockPanel.Styles>
+          <!-- Basisgröße der Icons als Style (nicht lokal), damit der Compact-Selector sie
+               überschreiben kann – lokale Werte hätten immer Vorrang vor Style-Settern. -->
+          <Style Selector="TextBlock.navicon">
+            <Setter Property="FontSize" Value="15"/>
+          </Style>
+          <!-- Minimierter Zustand: Icons größer & zentriert, Beschriftungen ausgeblendet -->
+          <Style Selector="DockPanel.compact TextBlock.navlabel">
+            <Setter Property="IsVisible" Value="False"/>
+          </Style>
+          <Style Selector="DockPanel.compact TextBlock.navicon">
+            <Setter Property="FontSize" Value="20"/>
+          </Style>
+          <Style Selector="DockPanel.compact Button.navitem">
+            <Setter Property="HorizontalContentAlignment" Value="Center"/>
+          </Style>
+          <Style Selector="DockPanel.compact TextBlock.navsection">
+            <Setter Property="IsVisible" Value="False"/>
+          </Style>
+          <Style Selector="DockPanel.compact TextBlock.appsubtitle">
+            <Setter Property="IsVisible" Value="False"/>
+          </Style>
+          <Style Selector="DockPanel.compact Border.appheader">
+            <Setter Property="HorizontalAlignment" Value="Center"/>
+          </Style>
+        </DockPanel.Styles>
 
         <Border DockPanel.Dock="Top" Padding="16,20,16,14"
                 BorderBrush="{DynamicResource SystemControlForegroundBaseLowBrush}"
                 BorderThickness="0,0,0,1">
-          <StackPanel>
-            <TextBlock Text="LehrerApp" FontSize="20" FontWeight="SemiBold"/>
-            <TextBlock Text="{Binding CurrentSchoolYear}"
-                       FontSize="12" Opacity="0.55" Margin="0,2,0,0"/>
+          <StackPanel Orientation="Horizontal" Spacing="10">
+            <Border Classes="appheader" Width="32" Height="32" CornerRadius="8"
+                    Background="{DynamicResource SystemControlBackgroundAccentBrush}">
+              <TextBlock Text="L" FontSize="16" FontWeight="Bold" Foreground="White"
+                         HorizontalAlignment="Center" VerticalAlignment="Center"/>
+            </Border>
+            <StackPanel Classes="appsubtitle" VerticalAlignment="Center">
+              <TextBlock Text="LehrerApp" FontSize="15" FontWeight="SemiBold"/>
+              <TextBlock Text="{Binding CurrentSchoolYear}"
+                         FontSize="11" Opacity="0.55"/>
+            </StackPanel>
           </StackPanel>
         </Border>
 
@@ -72,49 +105,84 @@
 
         <ScrollViewer>
           <StackPanel Margin="8,12,8,0" Spacing="2">
-            <Button Content="📊  Dashboard" HorizontalAlignment="Stretch"
+            <Button Classes="navitem" HorizontalAlignment="Stretch"
                     HorizontalContentAlignment="Left" Background="Transparent"
                     Padding="10,8" CornerRadius="6"
                     Command="{Binding NavigateToCommand}"
-                    CommandParameter="{x:Static vm:NavItem.Dashboard}"/>
+                    CommandParameter="{x:Static vm:NavItem.Dashboard}">
+              <StackPanel Orientation="Horizontal" Spacing="10">
+                <TextBlock Classes="navicon" Text="📊" Width="20" TextAlignment="Center"/>
+                <TextBlock Classes="navlabel" Text="Dashboard"/>
+              </StackPanel>
+            </Button>
 
-            <TextBlock Text="UNTERRICHT" FontSize="10" FontWeight="Bold"
+            <TextBlock Classes="navsection" Text="UNTERRICHT" FontSize="10" FontWeight="Bold"
                        Opacity="0.4" Margin="10,14,0,4"/>
 
-            <Button Content="🏫  Lerngruppen" HorizontalAlignment="Stretch"
+            <Button Classes="navitem" HorizontalAlignment="Stretch"
                     HorizontalContentAlignment="Left" Background="Transparent"
                     Padding="10,8" CornerRadius="6"
                     Command="{Binding NavigateToCommand}"
-                    CommandParameter="{x:Static vm:NavItem.Groups}"/>
-            <Button Content="👤  Schüler" HorizontalAlignment="Stretch"
+                    CommandParameter="{x:Static vm:NavItem.Groups}">
+              <StackPanel Orientation="Horizontal" Spacing="10">
+                <TextBlock Classes="navicon" Text="🏫" Width="20" TextAlignment="Center"/>
+                <TextBlock Classes="navlabel" Text="Lerngruppen"/>
+              </StackPanel>
+            </Button>
+            <Button Classes="navitem" HorizontalAlignment="Stretch"
                     HorizontalContentAlignment="Left" Background="Transparent"
                     Padding="10,8" CornerRadius="6"
                     Command="{Binding NavigateToCommand}"
-                    CommandParameter="{x:Static vm:NavItem.Students}"/>
-            <Button Content="📝  Klausuren" HorizontalAlignment="Stretch"
+                    CommandParameter="{x:Static vm:NavItem.Students}">
+              <StackPanel Orientation="Horizontal" Spacing="10">
+                <TextBlock Classes="navicon" Text="👤" Width="20" TextAlignment="Center"/>
+                <TextBlock Classes="navlabel" Text="Schüler"/>
+              </StackPanel>
+            </Button>
+            <Button Classes="navitem" HorizontalAlignment="Stretch"
                     HorizontalContentAlignment="Left" Background="Transparent"
                     Padding="10,8" CornerRadius="6"
                     Command="{Binding NavigateToCommand}"
-                    CommandParameter="{x:Static vm:NavItem.Exams}"/>
-            <Button Content="📅  Planung" HorizontalAlignment="Stretch"
+                    CommandParameter="{x:Static vm:NavItem.Exams}">
+              <StackPanel Orientation="Horizontal" Spacing="10">
+                <TextBlock Classes="navicon" Text="📝" Width="20" TextAlignment="Center"/>
+                <TextBlock Classes="navlabel" Text="Klausuren"/>
+              </StackPanel>
+            </Button>
+            <Button Classes="navitem" HorizontalAlignment="Stretch"
                     HorizontalContentAlignment="Left" Background="Transparent"
                     Padding="10,8" CornerRadius="6"
                     Command="{Binding NavigateToCommand}"
-                    CommandParameter="{x:Static vm:NavItem.Planner}"/>
+                    CommandParameter="{x:Static vm:NavItem.Planner}">
+              <StackPanel Orientation="Horizontal" Spacing="10">
+                <TextBlock Classes="navicon" Text="📅" Width="20" TextAlignment="Center"/>
+                <TextBlock Classes="navlabel" Text="Planung"/>
+              </StackPanel>
+            </Button>
 
-            <TextBlock Text="VERWALTUNG" FontSize="10" FontWeight="Bold"
+            <TextBlock Classes="navsection" Text="VERWALTUNG" FontSize="10" FontWeight="Bold"
                        Opacity="0.4" Margin="10,14,0,4"/>
 
-            <Button Content="⏱  Arbeitszeit" HorizontalAlignment="Stretch"
+            <Button Classes="navitem" HorizontalAlignment="Stretch"
                     HorizontalContentAlignment="Left" Background="Transparent"
                     Padding="10,8" CornerRadius="6"
                     Command="{Binding NavigateToCommand}"
-                    CommandParameter="{x:Static vm:NavItem.Workload}"/>
-            <Button Content="⚙️  Einstellungen" HorizontalAlignment="Stretch"
+                    CommandParameter="{x:Static vm:NavItem.Workload}">
+              <StackPanel Orientation="Horizontal" Spacing="10">
+                <TextBlock Classes="navicon" Text="⏱" Width="20" TextAlignment="Center"/>
+                <TextBlock Classes="navlabel" Text="Arbeitszeit"/>
+              </StackPanel>
+            </Button>
+            <Button Classes="navitem" HorizontalAlignment="Stretch"
                     HorizontalContentAlignment="Left" Background="Transparent"
                     Padding="10,8" CornerRadius="6"
                     Command="{Binding NavigateToCommand}"
-                    CommandParameter="{x:Static vm:NavItem.Settings}"/>
+                    CommandParameter="{x:Static vm:NavItem.Settings}">
+              <StackPanel Orientation="Horizontal" Spacing="10">
+                <TextBlock Classes="navicon" Text="⚙️" Width="20" TextAlignment="Center"/>
+                <TextBlock Classes="navlabel" Text="Einstellungen"/>
+              </StackPanel>
+            </Button>
           </StackPanel>
         </ScrollViewer>
       </DockPanel>