feat(12-02): add MSP logo section with live preview to SettingsView

- Add Separator and MSP Logo label after data folder section
- Add Border with Grid containing Image preview and placeholder TextBlock
- Image bound to MspLogoPreview via Base64ToImageConverter with max 80x240
- DataTrigger toggles placeholder visibility when logo is null
- Import/Clear buttons bound to BrowseMspLogoCommand/ClearMspLogoCommand
- StatusMessage TextBlock in red, visible only when set

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

SharepointToolbox/Views/Tabs/SettingsView.xaml

@@ -24,5 +24,40 @@
               Command="{Binding BrowseFolderCommand}" Width="80" Margin="8,0,0,0" />
       <TextBox Text="{Binding DataFolder, UpdateSourceTrigger=PropertyChanged}" />
     </DockPanel>
+
+    <Separator Margin="0,12" />
+
+    <!-- MSP Logo -->
+    <Label Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[settings.logo.title]}" />
+    <Border BorderBrush="#DDDDDD" BorderThickness="1" Padding="8" CornerRadius="4"
+            HorizontalAlignment="Left" MinWidth="200" MinHeight="60" Margin="0,4,0,0">
+      <Grid>
+        <Image Source="{Binding MspLogoPreview, Converter={StaticResource Base64ToImageConverter}}"
+               MaxHeight="80" MaxWidth="240" Stretch="Uniform" HorizontalAlignment="Left"
+               Visibility="{Binding MspLogoPreview, Converter={StaticResource StringToVisibilityConverter}}" />
+        <TextBlock Text="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[settings.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 MspLogoPreview, 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=[settings.logo.browse]}"
+              Command="{Binding BrowseMspLogoCommand}" Width="80" Margin="0,0,8,0" />
+      <Button Content="{Binding Source={x:Static loc:TranslationSource.Instance}, Path=[settings.logo.clear]}"
+              Command="{Binding ClearMspLogoCommand}" Width="80" />
+    </StackPanel>
+    <TextBlock Text="{Binding StatusMessage}" Foreground="#CC0000" FontSize="11" Margin="0,4,0,0"
+               Visibility="{Binding StatusMessage, Converter={StaticResource StringToVisibilityConverter}}" />
   </StackPanel>
 </UserControl>