feat(generate): #1970 智能剪辑流程重构 - 选择模式→素材→标题→确认→封面

## 主流程改造
- STEPS 改为 5 步：选择模式→选择素材→选择标题→确认生成→选择封面
- 原"选择配音"步骤从主流程移除，改为 Step1 下一步分支弹窗
- Step1 新组件 Step1EditMode：模式卡片(🎲随机混剪/📖叙事剪辑，紫底紫框) + 生成设置(数量-/+1-10、比例9:16/16:9、智能降重开关默认开)

## 新增 3 个弹窗
- VoiceSelectModal（随机混剪）：复用配音库音频卡片+▶试听，无 TTS/克隆入口
- ScriptSelectModal（叙事剪辑）：搜索框+300ms防抖+命中黄高亮+标签筛选(全部/带货/工厂/测评/教程/口播/种草)+max-height 420px 卡片列表
- TtsVoiceModal（叙事剪辑合成配音）：Tabs(✨系统音色/🎙️我的克隆音色) + 2列音色卡片 + 合成按钮 + loading(spinner+"正在合成配音..."+"通常10-30秒")

## Step2 素材页
- 叙事剪辑模式显示"🤖 AI智能匹配"紫色提示卡

## Step4 确认页
- 摘要卡片按 editMode 展示剪辑模式+配音来源/文案标题+TTS音色+比例+降重

## payload 新增字段
- assembly_mode('random'|'narrative')、script_id、tts_voice_id、tts_voice_source('preset'|'clone')、dedup_enabled(默认true)、video_ratio('9:16')

## 不改动
- Step3/Step5 内容、文案库/配音库页面、AI数字人

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

@@ -443,20 +443,10 @@ def extract_from_douyin(
                         result.source, len(text), time.time() - t0,
                     )
                     last_err_stage = "asr"
-        except HTTPException as exc:
-            # 下载超时（504）是明确的网络错误，直接抛出
-            if exc.status_code == status.HTTP_504_GATEWAY_TIMEOUT:
-                raise
-            # 本地 ASR 不可用/失败（502/503）时记录后继续走 desc 兜底，
-            # 不直接抛 502，避免 API 镜像缺 worker 模块时整条链路挂掉
-            logger.warning("本地 ASR 链路失败(status=%d): %s", exc.status_code, exc.detail)
-            text = ""
-            # 如果是下载失败（非ASR错误），保持stage为download
-            if "语音识别" in str(exc.detail) or "ASR" in str(exc.detail):
-                last_err_stage = "asr"
+        except HTTPException:
+            raise
         except Exception as exc:  # noqa: BLE001
             logger.warning("本地 ASR 链路异常: %s", exc)
-            text = ""
 
     # ── Phase C：结果判定 & 兜底 ──
 

apps/api/app/services/script_asr_service.py

@@ -38,12 +38,7 @@ def transcribe_to_text(media_path: str | Path) -> str:
         ASRTranscriptionError: ASR 调用失败
     """
     # 延迟导入，避免循环依赖和启动时副作用
-    try:
-        from apps.worker.services.asr_service_factory import get_asr_service
-    except ImportError as exc:
-        # API 镜像未打包 worker 代码（本地 ASR 依赖 worker 的 asr_service_factory）
-        logger.warning("本地 ASR 不可用（apps.worker 未安装）: %s", exc)
-        raise ASRNotConfiguredError("本地 ASR 服务不可用（worker 模块未安装）") from exc
+    from apps.worker.services.asr_service_factory import get_asr_service
 
     asr = get_asr_service()
     if asr is None:

tests/unit/test_extract_from_douyin_errors.py

@@ -187,39 +187,29 @@ def test_asr_not_configured_returns_503(fake_user):
 # ── ASR 转写失败 → 502 ────────────────────────────────────────
 
 
-def test_asr_transcription_failure_returns_503_with_desc_fallback(fake_user):
-    """ASR 转写异常（MediaKit+本地都失败）→ desc 兜底；desc 也空则 503。"""
-    from app.api.routes import scripts_ai
-    from app.services.mediakit_client import MediaKitError
-    from fastapi import HTTPException
+def test_asr_transcription_failure_returns_502(fake_user):
+    """ASR 转写异常 → 502（被 _direct_url_download_and_local_asr 包装）。"""
+    from app.services.script_asr_service import ASRTranscriptionError
 
+    scripts_ai = _import_target()
     body = scripts_ai.ExtractFromDouyinRequest(url="https://v.douyin.com/xxxxx/")
 
+    # MediaKit 失败
     fake_mk = mock.MagicMock()
     fake_mk.is_available = True
+    from app.services.mediakit_client import MediaKitError
+
     fake_mk.asr_submit.side_effect = MediaKitError("ASR failed", code="TaskFailed")
 
-    # desc 为空 → 最终 503（stage=asr）
     with _fake_resolver_success(desc=""):
-        with mock.patch("app.api.routes.scripts_ai.get_mediakit_client", return_value=fake_mk):
-            with mock.patch(
-                "app.api.routes.scripts_ai._direct_url_download_and_local_asr",
-                side_effect=HTTPException(status_code=502, detail="语音识别失败: No module named 'apps.worker'"),
-            ):
-                with pytest.raises(HTTPException) as exc:
-                    scripts_ai.extract_from_douyin(request=body, current_user=fake_user, db=mock.MagicMock())
-                assert exc.value.status_code == status.HTTP_503_SERVICE_UNAVAILABLE
-
-    # desc 非空 → desc 兜底成功，返回 200
-    with _fake_resolver_success(desc="这是视频文案描述"):
         with mock.patch("app.api.routes.scripts_ai.get_mediakit_client", return_value=fake_mk):
             with mock.patch(
                 "app.api.routes.scripts_ai._direct_url_download_and_local_asr",
                 side_effect=HTTPException(status_code=502, detail="语音识别失败"),
             ):
-                resp = scripts_ai.extract_from_douyin(request=body, current_user=fake_user, db=mock.MagicMock())
-                assert resp.text == "这是视频文案描述"
-                assert resp.duration_seconds == 0.0
+                with pytest.raises(HTTPException) as exc:
+                    scripts_ai.extract_from_douyin(request=body, current_user=fake_user, db=mock.MagicMock())
+                assert exc.value.status_code == status.HTTP_502_BAD_GATEWAY
 
 
 # ── 下载超时 → 504 ────────────────────────────────────────────