fix(player): persist player prefs outside quota-bound queue blob (#958)

* fix(player): persist volume/repeat in dedicated localStorage key

Player prefs were bundled with the full queue blob in psysonic-player; after
thin-state #872 a large queue can exceed the quota and safeStorage silently
drops every write, so volume and repeat mode stopped surviving restarts.
Move them to psysonic_player_prefs, gate main-blob writes until rehydrate,
and sync volume to the Rust engine on startup.

* fix(player): split queue visibility and Last.fm cache from main persist blob

Move isQueueVisible and lastfmLovedCache to dedicated localStorage keys so
they keep saving when psysonic-player hits the quota on large queues. Include
the new keys in settings backup export.

* docs: note player prefs persist fix in CHANGELOG and credits (PR #958)

src/store/lastfmLovedCacheStorage.ts

@@ -0,0 +1,55 @@
+/**
+ * Last.fm loved-track cache keyed by `${title}::${artist}`. Kept out of the
+ * main `psysonic-player` blob so a large queue cannot block writes (thin-state
+ * #872 quota issue). Same split-storage pattern as `playerPrefsStorage.ts`.
+ */
+const CACHE_STORAGE_KEY = 'psysonic_lastfm_loved_cache';
+const LEGACY_PLAYER_STORAGE_KEY = 'psysonic-player';
+
+function sanitizeCache(raw: unknown): Record<string, boolean> {
+  if (!raw || typeof raw !== 'object') return {};
+  const out: Record<string, boolean> = {};
+  for (const [key, value] of Object.entries(raw as Record<string, unknown>)) {
+    if (typeof key === 'string' && key.length > 0 && typeof value === 'boolean') {
+      out[key] = value;
+    }
+  }
+  return out;
+}
+
+function readLegacyCacheFromPlayerBlob(): Record<string, boolean> | null {
+  if (typeof window === 'undefined') return null;
+  try {
+    const raw = window.localStorage.getItem(LEGACY_PLAYER_STORAGE_KEY);
+    if (!raw) return null;
+    const parsed = JSON.parse(raw) as { state?: { lastfmLovedCache?: unknown } };
+    const cache = parsed.state?.lastfmLovedCache;
+    if (!cache) return null;
+    const sanitized = sanitizeCache(cache);
+    return Object.keys(sanitized).length > 0 ? sanitized : null;
+  } catch {
+    return null;
+  }
+}
+
+export function readInitialLastfmLovedCache(): Record<string, boolean> {
+  if (typeof window === 'undefined') return {};
+
+  try {
+    const raw = window.localStorage.getItem(CACHE_STORAGE_KEY);
+    if (raw) return sanitizeCache(JSON.parse(raw));
+  } catch {
+    // fall through to legacy blob / empty
+  }
+
+  return readLegacyCacheFromPlayerBlob() ?? {};
+}
+
+export function persistLastfmLovedCache(cache: Record<string, boolean>): void {
+  if (typeof window === 'undefined') return;
+  try {
+    window.localStorage.setItem(CACHE_STORAGE_KEY, JSON.stringify(sanitizeCache(cache)));
+  } catch {
+    // best-effort
+  }
+}