fix: initialize tracksCacheBytes on startup to enforce cache limit (#1951)

Previously, tracksCacheBytes was initialized to 0 and only updated when
entering the settings page. This caused the cache limit to not work until
the user manually opened settings. Now the cache size is calculated from
the database on app startup, ensuring cache cleanup triggers correctly.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: fatelove42

src/utils/db.js

@@ -30,6 +30,46 @@ db.version(1).stores({
 
 let tracksCacheBytes = 0;
 
+// 等待 settings 可用
+async function waitForSettingsReady(timeoutMs = 5000) {
+  const interval = 100;
+  const maxTries = Math.ceil(timeoutMs / interval);
+  let tries = 0;
+  while (
+    (store.state == null ||
+      store.state.settings == null ||
+      store.state.settings.cacheLimit === undefined) &&
+    tries < maxTries
+  ) {
+    await new Promise(resolve => setTimeout(resolve, interval));
+    tries++;
+  }
+  return store.state && store.state.settings;
+}
+
+// 初始化现有缓存总大小，确保应用启动时能正确判断并清理超限缓存
+async function initTracksCacheBytes() {
+  if (!process.env.IS_ELECTRON) return;
+  try {
+    await waitForSettingsReady();
+    const all = await db.trackSources.toArray();
+    tracksCacheBytes = all.reduce(
+      (sum, t) => sum + (t?.source?.byteLength || 0),
+      0
+    );
+    console.debug(
+      '[debug][db.js] initTracksCacheBytes, total bytes:',
+      tracksCacheBytes
+    );
+    deleteExcessCache();
+  } catch (err) {
+    console.debug('[debug][db.js] initTracksCacheBytes failed', err);
+  }
+}
+
+// 模块加载时触发初始化
+initTracksCacheBytes();
+
 async function deleteExcessCache() {
   if (
     store.state.settings.cacheLimit === false ||