feat(12-03): add client logo section with live preview to ProfileManagementDialog

- Increase dialog height from 480 to 620 to accommodate logo section
- Add new Row 3 with logo preview, Import/Clear/Pull from Entra buttons
- Image bound to ClientLogoPreview via Base64ToImageConverter
- Placeholder text shown when no logo configured via DataTrigger
- ValidationMessage displays feedback below logo buttons
- All logo buttons auto-disable when no profile selected

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

SharepointToolbox/Views/Dialogs/ProfileManagementDialog.xaml

@@ -2,7 +2,7 @@
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:loc="clr-namespace:SharepointToolbox.Localization"
-        Title="Manage Profiles" Width="500" Height="480"
+        Title="Manage Profiles" Width="500" Height="620"
         WindowStartupLocation="CenterOwner" ShowInTaskbar="False"
         ResizeMode="NoResize">
   <Grid Margin="12">
@@ -11,6 +11,7 @@
       <RowDefinition Height="*" />
       <RowDefinition Height="Auto" />
       <RowDefinition Height="Auto" />
+      <RowDefinition Height="Auto" />
     </Grid.RowDefinitions>
 
     <!-- Profile list -->
@@ -45,8 +46,45 @@
                Grid.Row="2" Grid.Column="1" Margin="0,2" />
     </Grid>
 
+    <!-- Client Logo -->
+    <StackPanel Grid.Row="3" Margin="0,8,0,8">
+      <Label Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[profile.logo.title]}" Padding="0,0,0,4" />
+      <Border BorderBrush="#DDDDDD" BorderThickness="1" Padding="8" CornerRadius="4"
+              HorizontalAlignment="Left" MinWidth="200" MinHeight="50">
+        <Grid>
+          <Image Source="{Binding ClientLogoPreview, Converter={StaticResource Base64ToImageConverter}}"
+                 MaxHeight="60" MaxWidth="200" Stretch="Uniform" HorizontalAlignment="Left"
+                 Visibility="{Binding ClientLogoPreview, Converter={StaticResource StringToVisibilityConverter}}" />
+          <TextBlock Text="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[profile.logo.nopreview]}"
+                     VerticalAlignment="Center" HorizontalAlignment="Center"
+                     Foreground="#999999" FontStyle="Italic">
+            <TextBlock.Style>
+              <Style TargetType="TextBlock">
+                <Setter Property="Visibility" Value="Visible" />
+                <Style.Triggers>
+                  <DataTrigger Binding="{Binding ClientLogoPreview, Converter={StaticResource StringToVisibilityConverter}}" Value="Visible">
+                    <Setter Property="Visibility" Value="Collapsed" />
+                  </DataTrigger>
+                </Style.Triggers>
+              </Style>
+            </TextBlock.Style>
+          </TextBlock>
+        </Grid>
+      </Border>
+      <StackPanel Orientation="Horizontal" Margin="0,6,0,0">
+        <Button Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[profile.logo.browse]}"
+                Command="{Binding BrowseClientLogoCommand}" Width="80" Margin="0,0,8,0" />
+        <Button Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[profile.logo.clear]}"
+                Command="{Binding ClearClientLogoCommand}" Width="80" Margin="0,0,8,0" />
+        <Button Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[profile.logo.autopull]}"
+                Command="{Binding AutoPullClientLogoCommand}" Width="130" />
+      </StackPanel>
+      <TextBlock Text="{Binding ValidationMessage}" Foreground="#CC0000" FontSize="11" Margin="0,4,0,0"
+                 Visibility="{Binding ValidationMessage, Converter={StaticResource StringToVisibilityConverter}}" />
+    </StackPanel>
+
     <!-- Buttons -->
-    <StackPanel Grid.Row="3" Orientation="Horizontal" HorizontalAlignment="Right">
+    <StackPanel Grid.Row="4" Orientation="Horizontal" HorizontalAlignment="Right">
       <Button Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[profile.add]}"
               Command="{Binding AddCommand}" Width="60" Margin="4,0" />
       <Button Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[profile.rename]}"