feat(flutter): library screen with 5 tabs (Artists/Albums/History/Liked/Hidden)

Models:
- history_event.dart (HistoryEvent + HistoryPage envelope)
- quarantine_mine.dart (QuarantineMineRow for /api/quarantine/mine)
- Renamed Page<T> -> Paged<T> to avoid collision with Material's Page

Endpoints:
- library_lists.dart: listArtists / listAlbums (paged)
- me.dart: history + quarantineMine
- likes.dart: extended with listTracks/Albums/Artists (paged)

UI:
- library_screen.dart: TabBar over 5 tabs
- Artists tab: 3-col grid
- Albums tab: 2-col grid
- History tab: list with relative-time formatting (matches HistoryRow.svelte)
- Liked tab: 3 stacked sections (artists scroll-row, albums scroll-row, tracks list)
- Hidden tab: list of quarantined tracks with reason pill
- /library route + library_music icon on home AppBar

First page only for v1 (limit 50). Infinite scroll deferred.

flutter_client/lib/models/history_event.dart

@@ -0,0 +1,44 @@
+import 'track.dart';
+
+/// Mirrors web/src/lib/api/history.ts HistoryEvent. Server emits
+/// `{events, has_more}` rather than the standard `Page<T>` envelope —
+/// history is timestamp-keyed so total isn't meaningful, only "more
+/// pages exist below."
+class HistoryEvent {
+  const HistoryEvent({
+    required this.id,
+    required this.playedAt,
+    required this.track,
+  });
+
+  final String id;
+  /// RFC3339 timestamp; UI formats relative ("3h ago" / "Tue 14:32" /
+  /// "May 1, 2025") via formatRelative helper.
+  final String playedAt;
+  final TrackRef track;
+
+  factory HistoryEvent.fromJson(Map<String, dynamic> j) => HistoryEvent(
+        id: j['id'] as String? ?? '',
+        playedAt: j['played_at'] as String? ?? '',
+        track: TrackRef.fromJson(
+          (j['track'] as Map?)?.cast<String, dynamic>() ?? const {},
+        ),
+      );
+}
+
+class HistoryPage {
+  const HistoryPage({required this.events, required this.hasMore});
+
+  final List<HistoryEvent> events;
+  final bool hasMore;
+
+  factory HistoryPage.fromJson(Map<String, dynamic> j) {
+    final raw = (j['events'] as List?) ?? const [];
+    return HistoryPage(
+      events: raw
+          .map((e) => HistoryEvent.fromJson((e as Map).cast<String, dynamic>()))
+          .toList(growable: false),
+      hasMore: j['has_more'] as bool? ?? false,
+    );
+  }
+}