refactor(ui): Lucide migration unit 2 — Icons.* -> LucideIcons.* sweep (#60)

Mechanical sweep across 30 files: every Material Icons.* replaced with
the signed-off Lucide equivalent + a flutter_lucide import per file.
Zero Material Icons.* remain in lib/; no unused imports.

Judgment-call mappings: album->disc_3, library_music->library_big,
playlist_play->list_video, graphic_eq->audio_lines,
system_update->download, restore->archive_restore,
download_done->circle_check_big.

track_actions_sheet like menu row: collapsed `liked ? favorite :
favorite_border` to a single LucideIcons.heart (the row's Like/Unlike
text label conveys state). Icon-only LikeButton + the notification keep
the filled-vs-outline shape per the design decision.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

flutter_client/lib/shared/widgets/main_app_bar_actions.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_lucide/flutter_lucide.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
@@ -26,27 +27,27 @@ class MainAppBarActions extends ConsumerWidget {
         if (currentRoute != '/home')
           IconButton(
             key: const Key('app_bar_home'),
-            icon: Icon(Icons.home, color: fs.parchment),
+            icon: Icon(LucideIcons.house, color: fs.parchment),
             tooltip: 'Home',
             onPressed: () => context.go('/home'),
           ),
         if (currentRoute != '/library')
           IconButton(
             key: const Key('app_bar_library'),
-            icon: Icon(Icons.library_music, color: fs.parchment),
+            icon: Icon(LucideIcons.library_big, color: fs.parchment),
             tooltip: 'Library',
             onPressed: () => context.push('/library'),
           ),
         if (currentRoute != '/search')
           IconButton(
             key: const Key('app_bar_search'),
-            icon: Icon(Icons.search, color: fs.parchment),
+            icon: Icon(LucideIcons.search, color: fs.parchment),
             tooltip: 'Search',
             onPressed: () => context.push('/search'),
           ),
         PopupMenuButton<String>(
           key: const Key('app_bar_overflow'),
-          icon: Icon(Icons.more_vert, color: fs.parchment),
+          icon: Icon(LucideIcons.ellipsis_vertical, color: fs.parchment),
           tooltip: 'More',
           onSelected: (route) => context.push(route),
           itemBuilder: (_) => [