feat: add theme mode support with AppThemeMode enum and AppThemeState service

- Introduced AppThemeMode enum to define theme options: System, Light, Dark.
- Updated AppSettingsDocument to include ThemeMode property.
- Created AppThemeState service to manage current theme mode and handle changes.
- Integrated theme mode handling in CouchbaseLiteAppSettingsService for persistence.
- Added JavaScript for theme management in the frontend, supporting system preference detection.
- Enhanced CSS with theme variables for consistent styling across light and dark modes.
- Updated Playwright tests to ensure sidebar functionality and responsiveness.

Components/Pages/CalendarView.razor

@@ -10,6 +10,7 @@
 
 <PageTitle>Calendar</PageTitle>
 
+<div class="calendar-page">
 <h1>Calendar</h1>
 
 <div class="d-flex align-items-center gap-2 mb-3">
@@ -51,11 +52,11 @@ else
                         {
                             @if (cell is null)
                             {
-                                <td class="calendar-cell bg-light"></td>
+                                <td class="calendar-cell calendar-cell-empty"></td>
                             }
                             else
                             {
-                                <td class="calendar-cell @GetCellClass(cell) @(IsActiveCell(cell.Date) ? "calendar-cell-active" : string.Empty)" @onclick="() => TogglePopup(cell.Date)" role="button">
+                                <td class="calendar-cell @GetCellClass(cell) @(IsToday(cell.Date) ? "calendar-cell-today" : string.Empty) @(IsActiveCell(cell.Date) ? "calendar-cell-active" : string.Empty)" @onclick="() => TogglePopup(cell.Date)" role="button">
                                     <div class="calendar-day-number">@cell.Date.Day</div>
 
                                     @foreach (var workUnit in cell.Entry?.WorkUnits ?? [])
@@ -193,6 +194,7 @@ else
         </div>
     }
 }
+</div>
 
 @code {
     [Parameter] public string? YearMonth { get; set; }
@@ -306,6 +308,8 @@ else
 
     private bool IsActiveCell(DateOnly date) => activeDate == date;
 
+    private static bool IsToday(DateOnly date) => date == DateOnly.FromDateTime(DateTime.Today);
+
     private void CreateWorkUnit(DateOnly date)
     {
         Navigation.NavigateTo($"/work-unit/{date:yyyy-MM-dd}");