feat(mobile): add album description functionality (#18886)

* feat(mobile): add album description functionality

- Introduced a new optional `description` field in the `Album` entity.
- Updated `AlbumViewerPageState` to manage `editDescriptionText`.
- Created `AlbumDescription` and `AlbumViewerEditableDescription` widgets for displaying and editing album descriptions.
- Enhanced `CreateAlbumPage` to include a description input field.
- Implemented backend support for updating album descriptions in `AlbumApiRepository` and `AlbumService`.
- Updated sync logic to handle album descriptions during data synchronization.
- Adjusted UI components to accommodate the new description feature.

* fix dart analysis error

* remove comment that shouldn't be there

* Album header styling

* fix: disable edit after album creation

---------

Co-authored-by: Alex <alex.tran1502@gmail.com>

mobile/lib/pages/album/album_viewer.dart

@@ -10,6 +10,7 @@ import 'package:immich_mobile/extensions/build_context_extensions.dart';
 import 'package:immich_mobile/models/albums/asset_selection_page_result.model.dart';
 import 'package:immich_mobile/pages/album/album_control_button.dart';
 import 'package:immich_mobile/pages/album/album_date_range.dart';
+import 'package:immich_mobile/pages/album/album_description.dart';
 import 'package:immich_mobile/pages/album/album_shared_user_icons.dart';
 import 'package:immich_mobile/pages/album/album_title.dart';
 import 'package:immich_mobile/providers/album/album.provider.dart';
@@ -36,6 +37,7 @@ class AlbumViewer extends HookConsumerWidget {
     }
 
     final titleFocusNode = useFocusNode();
+    final descriptionFocusNode = useFocusNode();
     final userId = ref.watch(authProvider).userId;
     final isMultiselecting = ref.watch(multiselectProvider);
     final isProcessing = useProcessingOverlay();
@@ -106,23 +108,44 @@ class AlbumViewer extends HookConsumerWidget {
         MultiselectGrid(
           key: const ValueKey("albumViewerMultiselectGrid"),
           renderListProvider: albumTimelineProvider(album.id),
-          topWidget: Column(
-            mainAxisAlignment: MainAxisAlignment.end,
-            crossAxisAlignment: CrossAxisAlignment.start,
-            children: [
-              AlbumTitle(
-                key: const ValueKey("albumTitle"),
-                titleFocusNode: titleFocusNode,
+          topWidget: Container(
+            decoration: BoxDecoration(
+              gradient: LinearGradient(
+                begin: Alignment.topCenter,
+                end: Alignment.bottomCenter,
+                colors: [
+                  context.primaryColor.withValues(alpha: 0.04),
+                  context.primaryColor.withValues(alpha: 0.02),
+                  Colors.orange.withValues(alpha: 0.02),
+                  Colors.transparent,
+                ],
+                stops: const [0.0, 0.3, 0.7, 1.0],
               ),
-              const AlbumDateRange(),
-              const AlbumSharedUserIcons(),
-              if (album.isRemote)
-                AlbumControlButton(
-                  key: const ValueKey("albumControlButton"),
-                  onAddPhotosPressed: onAddPhotosPressed,
-                  onAddUsersPressed: onAddUsersPressed,
+            ),
+            child: Column(
+              mainAxisAlignment: MainAxisAlignment.end,
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: [
+                const SizedBox(height: 32),
+                const AlbumDateRange(),
+                AlbumTitle(
+                  key: const ValueKey("albumTitle"),
+                  titleFocusNode: titleFocusNode,
                 ),
-            ],
+                AlbumDescription(
+                  key: const ValueKey("albumDescription"),
+                  descriptionFocusNode: descriptionFocusNode,
+                ),
+                const AlbumSharedUserIcons(),
+                if (album.isRemote)
+                  AlbumControlButton(
+                    key: const ValueKey("albumControlButton"),
+                    onAddPhotosPressed: onAddPhotosPressed,
+                    onAddUsersPressed: onAddUsersPressed,
+                  ),
+                const SizedBox(height: 8),
+              ],
+            ),
           ),
           onRemoveFromAlbum: onRemoveFromAlbumPressed,
           editEnabled: album.ownerId == userId,
@@ -136,6 +159,7 @@ class AlbumViewer extends HookConsumerWidget {
           child: AlbumViewerAppbar(
             key: const ValueKey("albumViewerAppbar"),
             titleFocusNode: titleFocusNode,
+            descriptionFocusNode: descriptionFocusNode,
             userId: userId,
             onAddPhotos: onAddPhotosPressed,
             onAddUsers: onAddUsersPressed,