feat(web): per-platform source tabs on Home and Library

Recommend playlists, daily songs, and user playlists on Home now show
a [网易云][QQ] tab when both platforms are logged in. Library 我的歌单
gets the same tab. Selection persists per-section in localStorage and
falls back gracefully when the persisted source becomes unavailable
(e.g., user logged out). Removes dead 我的收藏 block from Library that
referenced a non-existent /api/music/user/liked endpoint.

Spec: docs/superpowers/specs/2026-05-06-music-source-tabs-design.md

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

web/src/stores/sourceTabs.ts

@@ -0,0 +1,36 @@
+import type { Source } from './player.js';
+
+const STORAGE_KEY = 'source-tabs';
+
+export type TabKey =
+  | 'home.recommend'
+  | 'home.daily'
+  | 'home.user'
+  | 'library.user';
+
+function readAll(): Partial<Record<TabKey, Source>> {
+  try {
+    const raw = localStorage.getItem(STORAGE_KEY);
+    if (!raw) return {};
+    const parsed = JSON.parse(raw);
+    return typeof parsed === 'object' && parsed !== null ? parsed : {};
+  } catch {
+    return {};
+  }
+}
+
+export function loadTabSource(key: TabKey, fallback: Source = 'netease'): Source {
+  const all = readAll();
+  const v = all[key];
+  return v === 'netease' || v === 'qq' ? v : fallback;
+}
+
+export function saveTabSource(key: TabKey, value: Source): void {
+  try {
+    const all = readAll();
+    all[key] = value;
+    localStorage.setItem(STORAGE_KEY, JSON.stringify(all));
+  } catch {
+    // localStorage may be unavailable (private browsing); silently no-op
+  }
+}