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/settings/about_section.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:package_info_plus/package_info_plus.dart';
 
@@ -88,7 +89,7 @@ class _AboutSectionState extends ConsumerState<AboutSection> {
         padding: const EdgeInsets.fromLTRB(16, 0, 16, 4),
         child: Row(
           children: [
-            Icon(Icons.info_outline, color: fs.parchment, size: 18),
+            Icon(LucideIcons.info, color: fs.parchment, size: 18),
             const SizedBox(width: 8),
             Text('Installed version',
                 style: TextStyle(color: fs.parchment, fontSize: 14)),
@@ -105,7 +106,7 @@ class _AboutSectionState extends ConsumerState<AboutSection> {
         padding: const EdgeInsets.fromLTRB(16, 4, 16, 4),
         child: Row(
           children: [
-            Icon(Icons.cloud_outlined, color: fs.parchment, size: 18),
+            Icon(LucideIcons.cloud, color: fs.parchment, size: 18),
             const SizedBox(width: 8),
             Text('Latest version',
                 style: TextStyle(color: fs.parchment, fontSize: 14)),
@@ -148,7 +149,7 @@ class _AboutSectionState extends ConsumerState<AboutSection> {
                         valueColor: AlwaysStoppedAnimation(fs.parchment),
                       ),
                     )
-                  : const Icon(Icons.refresh, size: 18),
+                  : const Icon(LucideIcons.refresh_cw, size: 18),
               label: Text(_checking ? 'Checking…' : 'Check for updates'),
             ),
             if (hasUpdate) ...[
@@ -172,7 +173,7 @@ class _AboutSectionState extends ConsumerState<AboutSection> {
                           valueColor: AlwaysStoppedAnimation(fs.parchment),
                         ),
                       )
-                    : const Icon(Icons.system_update, size: 18),
+                    : const Icon(LucideIcons.download, size: 18),
                 label: Text(
                   _installStage == _InstallStage.downloading
                       ? 'Downloading…'