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/Layout/MainLayout.razor.css

@@ -14,8 +14,8 @@ main {
 }
 
 .top-row {
-    background-color: #f7f7f7;
-    border-bottom: 1px solid #d6d5d5;
+    background-color: var(--wt-header-bg);
+    border-bottom: 1px solid var(--wt-header-border);
     justify-content: flex-end;
     height: 3.5rem;
     display: flex;
@@ -23,6 +23,7 @@ main {
 }
 
     .top-row ::deep a, .top-row ::deep .btn-link {
+        color: var(--wt-header-link);
         white-space: nowrap;
         margin-left: 1.5rem;
         text-decoration: none;
@@ -37,30 +38,9 @@ main {
         text-overflow: ellipsis;
     }
 
-.sidebar-toggle {
-    display: none;
-    align-items: center;
-    justify-content: center;
-    flex-direction: column;
-    gap: 0.2rem;
-    width: 2.5rem;
-    height: 2.5rem;
-    margin-right: auto;
-    border: 1px solid #d6d5d5;
-    border-radius: 0.65rem;
-    background: #fff;
-}
-
-.sidebar-toggle-bar {
-    width: 1rem;
-    height: 2px;
-    background: #334155;
-    border-radius: 999px;
-}
-
 @media (max-width: 640.98px) {
     .top-row {
-        justify-content: space-between;
+        justify-content: flex-end;
     }
 
     .top-row ::deep a, .top-row ::deep .btn-link {
@@ -100,10 +80,6 @@ main {
         padding-right: 1.5rem !important;
     }
 
-    .sidebar-toggle {
-        display: inline-flex;
-    }
-
     .sidebar.sidebar-collapsed {
         width: 5rem;
     }