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/admin/admin_landing_screen.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';
 
@@ -34,7 +35,7 @@ class AdminLandingScreen extends ConsumerWidget {
               children: [
                 AdminSectionCard(
                   key: const Key('admin_card_requests'),
-                  icon: Icons.inbox,
+                  icon: LucideIcons.inbox,
                   title: 'Requests',
                   subtitle: 'Approve or reject Lidarr requests',
                   count: c.requests,
@@ -42,7 +43,7 @@ class AdminLandingScreen extends ConsumerWidget {
                 ),
                 AdminSectionCard(
                   key: const Key('admin_card_quarantine'),
-                  icon: Icons.warning_amber,
+                  icon: LucideIcons.triangle_alert,
                   title: 'Quarantine',
                   subtitle: 'Resolve scan failures',
                   count: c.quarantine,
@@ -50,7 +51,7 @@ class AdminLandingScreen extends ConsumerWidget {
                 ),
                 AdminSectionCard(
                   key: const Key('admin_card_users'),
-                  icon: Icons.people,
+                  icon: LucideIcons.users,
                   title: 'Users',
                   subtitle: 'Manage accounts and invites',
                   count: c.users,

flutter_client/lib/admin/admin_users_screen.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_lucide/flutter_lucide.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
@@ -59,7 +60,7 @@ class AdminUsersScreen extends ConsumerWidget {
                 trailing: TextButton.icon(
                   key: const Key('invite_generate_button'),
                   onPressed: () => _showGenerateInvite(context, ref),
-                  icon: Icon(Icons.add, color: fs.parchment),
+                  icon: Icon(LucideIcons.plus, color: fs.parchment),
                   label: Text('Generate',
                       style: TextStyle(color: fs.parchment)),
                 ),

flutter_client/lib/admin/widgets/admin_quarantine_row.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_lucide/flutter_lucide.dart';
 
 import '../../models/admin_quarantine_item.dart';
 import '../../theme/theme_extension.dart';
@@ -45,7 +46,7 @@ class AdminQuarantineRow extends StatelessWidget {
       ),
       trailing: PopupMenuButton<String>(
         key: Key('admin_quarantine_menu_${item.trackId}'),
-        icon: Icon(Icons.more_vert, color: fs.parchment),
+        icon: Icon(LucideIcons.ellipsis_vertical, color: fs.parchment),
         onSelected: (action) async {
           switch (action) {
             case 'resolve':

flutter_client/lib/admin/widgets/admin_user_row.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_lucide/flutter_lucide.dart';
 
 import '../../models/admin_user.dart';
 import '../../theme/theme_extension.dart';
@@ -29,7 +30,7 @@ class AdminUserRow extends StatelessWidget {
             _Badge(label: 'auto-approve', color: fs.moss),
         ],
       ),
-      trailing: Icon(Icons.chevron_right, color: fs.ash),
+      trailing: Icon(LucideIcons.chevron_right, color: fs.ash),
       onTap: onTap,
     );
   }

flutter_client/lib/admin/widgets/invite_row.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_lucide/flutter_lucide.dart';
 import 'package:flutter/services.dart';
 
 import '../../models/invite.dart';
@@ -31,7 +32,7 @@ class InviteRow extends StatelessWidget {
             ),
           ),
           IconButton(
-            icon: Icon(Icons.copy, color: fs.ash, size: 18),
+            icon: Icon(LucideIcons.copy, color: fs.ash, size: 18),
             tooltip: 'Copy',
             onPressed: () =>
                 Clipboard.setData(ClipboardData(text: invite.token)),
@@ -63,7 +64,7 @@ class InviteRow extends StatelessWidget {
         ],
       ),
       trailing: IconButton(
-        icon: Icon(Icons.delete_outline, color: fs.oxblood),
+        icon: Icon(LucideIcons.trash_2, color: fs.oxblood),
         tooltip: 'Revoke',
         onPressed: onRevoke,
       ),