Switch to user Chrome CDP for YouTube transcript, fix auth and ads

- Replace Playwright standalone browser with CDP connection to user Chrome
  (bypasses YouTube bot detection by using logged-in Chrome session)
- Add video playback, ad detection/skip, and play confirmation before transcript extraction
- Extract transcript JS to separate resource files (fix SyntaxError in evaluate)
- Add ytInitialPlayerResponse-based transcript extraction as primary method
- Fix token refresh: retry on network error during backend restart
- Fix null userId logout, CLOB type hint for structured_content
- Disable XFCE screen lock/screensaver
- Add troubleshooting entries (#10-12) and YouTube transcript guide

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

sundol-frontend/src/lib/api.ts

@@ -68,9 +68,23 @@ api.interceptors.response.use(
     isRefreshing = true;
     originalRequest._retry = true;
 
+    const attemptRefresh = async (retryCount: number): Promise<string> => {
+      try {
+        const res = await api.post<LoginResponse>("/api/auth/refresh");
+        return res.data.accessToken;
+      } catch (err) {
+        const isNetworkError = !((err as AxiosError).response);
+        if (isNetworkError && retryCount < 2) {
+          // 네트워크 에러(서버 재시작 등)면 3초 후 재시도
+          await new Promise((r) => setTimeout(r, 3000));
+          return attemptRefresh(retryCount + 1);
+        }
+        throw err;
+      }
+    };
+
     try {
-      const res = await api.post<LoginResponse>("/api/auth/refresh");
-      const newToken = res.data.accessToken;
+      const newToken = await attemptRefresh(0);
 
       api.defaults.headers.common["Authorization"] = `Bearer ${newToken}`;
       onTokenRefreshed?.(newToken);