feat: responsive layout tuning, cache management page, and improved recent access UX

- Add responsive scaling across album, artist, playlist, downloaded album, local album, queue, setup, and tutorial screens to prevent overflow on smaller devices
- Add new Storage & Cache management page (Settings > Storage & Cache) with per-category clear and cleanup actions
- Extract normalizedHeaderTopPadding utility for consistent app bar padding
- Improve home search Recent Access behavior: show when focused with empty input, hide stale results during active recent mode
- Add excluded-downloaded-count tracking to local library scan stats
- Add recentEmpty and recentShowAllDownloads l10n keys (EN + ID)
- Add full cache management l10n keys (EN + ID)
- Fix about_page indentation and formatting consistency
- Fix appearance_settings_page formatting
- Fix downloaded_album_screen and local_album_screen formatting and responsive sizing

lib/widgets/collapsing_header.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:spotiflac_android/utils/app_bar_layout.dart';
 
 /// A collapsing header widget
 /// Title collapses from large to small when scrolling
@@ -19,7 +20,7 @@ class CollapsingHeader extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final colorScheme = Theme.of(context).colorScheme;
-    final topPadding = MediaQuery.of(context).padding.top;
+    final topPadding = normalizedHeaderTopPadding(context);
 
     return CustomScrollView(
       slivers: [