fix(douyin): ASR返回空时（无旁白视频）使用Feed desc兜底，避免503

apps/api/app/api/routes/scripts_ai.py

@@ -356,7 +356,7 @@ def _fetch_ttwid():
     # 方式一：直接调 ttwid 注册接口
     try:
         with httpx.Client(timeout=8, follow_redirects=True, verify=False) as http:
-            http.post(
+            r = http.post(
                 "https://ttwid.bytedance.com/ttwid/union/register/",
                 json={
                     "region": "cn",
@@ -769,7 +769,7 @@ def _ytdlp_download_and_local_asr(page_url, temp_dir, cookiefile=None):
         cookie_files_to_try.append(cookiefile)
 
     # 2. 合成 cookie 重试（复用 _ytdlp_extract 的 cookie 生成逻辑，8次重试）
-    import time as _time
+    import secrets, time as _time
     ttwid = _fetch_ttwid()
     for i in range(8):
         if i % 3 == 0:
@@ -945,10 +945,9 @@ def _html_scrape_direct_url(page_url, timeout=15):
 @router.get("/douyin/__debug_diag")
 def douyin_diag():
     """[Staging only] 容器内网络/yt-dlp诊断"""
-    import tempfile as _tf
-    import time as _t
-
     import httpx as _httpx
+    import time as _t
+    import tempfile as _tf
     import yt_dlp as _ytdlp
 
     results = {}
@@ -1244,17 +1243,31 @@ def extract_from_douyin(
         if text:
             break
 
+        # ASR 可能返回空（视频无旁白/只有BGM/环境音），此时用 feed_desc 作为文案兜底
+        if feed_desc and not text:
+            text = feed_desc.strip()
+            logger.info(
+                "抖音 ASR 未识别到语音（第%d轮），使用 Feed API desc 作为文案: desc_len=%d",
+                round_idx + 1, len(text),
+            )
+            break
+
         # 本轮全链路失败，等一下重试（直链未拿到可能是瞬时限流）
         if round_idx < max_rounds - 1:
             logger.info("第%d轮全链路失败，等待后重试", round_idx + 1)
             time.sleep(1.5)
 
     if not text:
-        logger.warning("抖音文案提取全部失败: url=%s", page_url)
-        raise HTTPException(
-            status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
-            detail="抖音链接解析暂时不可用，请稍后重试或手动输入文案",
-        )
+        # 终极兜底：所有 ASR 路径均失败/返回空时，若 Feed API 拿到了 desc 就直接用
+        if feed_desc:
+            text = feed_desc.strip()
+            logger.info("抖音所有 ASR 路径均失败，最终使用 Feed desc 作为文案: desc_len=%d", len(text))
+        else:
+            logger.warning("抖音文案提取全部失败: url=%s", page_url)
+            raise HTTPException(
+                status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
+                detail="抖音链接解析暂时不可用，请稍后重试或手动输入文案",
+            )
 
     return ExtractFromDouyinResponse(
         text=text,