chore: album's header styling (#18930)

mobile/lib/pages/album/album_viewer.dart

@@ -114,9 +114,9 @@ class AlbumViewer extends HookConsumerWidget {
                 begin: Alignment.topCenter,
                 end: Alignment.bottomCenter,
                 colors: [
+                  context.primaryColor.withValues(alpha: 0.06),
                   context.primaryColor.withValues(alpha: 0.04),
-                  context.primaryColor.withValues(alpha: 0.02),
-                  Colors.orange.withValues(alpha: 0.02),
+                  Colors.indigo.withValues(alpha: 0.02),
                   Colors.transparent,
                 ],
                 stops: const [0.0, 0.3, 0.7, 1.0],

mobile/lib/widgets/album/album_action_filled_button.dart

@@ -17,11 +17,15 @@ class AlbumActionFilledButton extends StatelessWidget {
   Widget build(BuildContext context) {
     return Padding(
       padding: const EdgeInsets.only(right: 8.0),
-      child: FilledButton.icon(
-        style: FilledButton.styleFrom(
+      child: OutlinedButton.icon(
+        style: OutlinedButton.styleFrom(
           padding: const EdgeInsets.symmetric(vertical: 0, horizontal: 16),
-          shape: RoundedRectangleBorder(
-            borderRadius: BorderRadius.circular(25),
+          shape: const RoundedRectangleBorder(
+            borderRadius: BorderRadius.all(Radius.circular(20)),
+          ),
+          side: BorderSide(
+            color: context.colorScheme.surfaceContainerHighest,
+            width: 1,
           ),
           backgroundColor: context.colorScheme.surfaceContainerHigh,
         ),

mobile/lib/widgets/album/album_viewer_appbar.dart

@@ -326,6 +326,7 @@ class AlbumViewerAppbar extends HookConsumerWidget
 
     return AppBar(
       elevation: 0,
+      backgroundColor: context.scaffoldBackgroundColor,
       leading: buildLeadingButton(),
       centerTitle: false,
       actions: [

mobile/lib/widgets/album/album_viewer_editable_description.dart

@@ -55,7 +55,7 @@ class AlbumViewerEditableDescription extends HookConsumerWidget {
           }
         },
         focusNode: descriptionFocusNode,
-        style: context.textTheme.bodyMedium,
+        style: context.textTheme.bodyLarge,
         maxLines: 3,
         minLines: 1,
         controller: descriptionTextEditController,