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/library/library_screen.dart

@@ -2,6 +2,7 @@ import 'dart:convert';
 
 import 'package:drift/drift.dart' as drift;
 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';
 
@@ -382,7 +383,7 @@ class _LibraryScreenState extends ConsumerState<LibraryScreen>
           IconButton(
             key: const Key('shuffle_all_button'),
             tooltip: 'Shuffle all',
-            icon: Icon(Icons.shuffle, color: fs.parchment),
+            icon: Icon(LucideIcons.shuffle, color: fs.parchment),
             onPressed: () async {
               final messenger = ScaffoldMessenger.of(context);
               final refs = await ref.read(shuffleSourceProvider).tracks();
@@ -866,7 +867,7 @@ class _QuarantineTile extends ConsumerWidget {
         ),
         IconButton(
           tooltip: 'Unhide',
-          icon: Icon(Icons.restore, color: fs.ash, size: 20),
+          icon: Icon(LucideIcons.archive_restore, color: fs.ash, size: 20),
           onPressed: () async {
             try {
               await ref.read(myQuarantineProvider.notifier).unflag(row.trackId);