fix: 确认生成兜底增强 — project_id 为空时通过 user_id 查找素材

根因：模板编辑器直接创建的草稿 plan 没有 project_id 和 config.asset_ids，
导致 _auto_fallback_auto_material_mode 跳过素材分配，
can_generate 报 "没有可渲染的就绪片段"。

修复：
- asset_repository 新增 find_ready_videos_by_user 方法
- _auto_fallback_auto_material_mode 增加策略2：project_id 为空时
  通过 uploaded_by_user_id 查找用户上传的就绪视频
- generation.py 传递 current_user.user.id 给兜底函数

apps/api/app/api/routes/templates_editor/_fallback.py

@@ -161,43 +161,74 @@ def _auto_fallback_auto_material_mode(
     clips_without_asset: list,
     asset_library_repo: Any,
     asset_repo: Any,
+    user_id: str = "",
 ) -> None:
-    """自动兜底 4: 项目有视频素材库时自动选素材"""
+    """自动兜底 4: 自动选素材分配给无素材片段
+    
+    查找策略（按优先级）：
+    1. plan 有 project_id → 从项目素材库查找
+    2. plan 无 project_id 但有 user_id → 从用户上传的素材中查找
+    """
     if not clips_without_asset:
         return
-    if not plan_check.project_id:
+
+    ready_videos: list = []
+    source_desc = ""
+
+    # 策略 1: 通过 project_id 查找项目素材库
+    if plan_check.project_id:
+        libs = asset_library_repo.find_by_project(plan_check.project_id)
+        video_lib = None
+        for lib in libs:
+            lib_kind = lib.kind.value if hasattr(lib.kind, "value") else lib.kind
+            if lib_kind == "video":
+                video_lib = lib
+                break
+        if video_lib:
+            assets = asset_repo.find_by_library(video_lib.id)
+            ready_videos = [
+                a
+                for a in assets
+                if (a.status.value if hasattr(a.status, "value") else a.status) == "ready"
+                and a.mime_type
+                and a.mime_type.startswith("video")
+            ]
+            source_desc = f"素材库 {video_lib.name}"
+
+    # 策略 2: 通过 user_id 查找用户上传的素材
+    if not ready_videos and user_id and hasattr(asset_repo, "find_ready_videos_by_user"):
+        logger.info(
+            "模板编辑器自动兜底4: plan=%s project_id 为空，尝试通过 user_id=%s 查找素材",
+            plan_id,
+            user_id,
+        )
+        ready_videos = asset_repo.find_ready_videos_by_user(user_id)
+        source_desc = f"用户上传 (user_id={user_id[:8]}...)"
+
+    if not ready_videos:
+        logger.warning(
+            "模板编辑器自动兜底4: plan=%s 未找到可用素材 (project_id=%s, user_id=%s)",
+            plan_id,
+            plan_check.project_id or "(empty)",
+            user_id[:8] + "..." if user_id else "(empty)",
+        )
         return
 
     logger.info(
-        "模板编辑器自动兜底4: plan=%s 自动选素材分配给 %d 个无素材片段",
+        "模板编辑器自动兜底4: plan=%s 自动选素材分配给 %d 个无素材片段 (来源: %s, 共 %d 个)",
         plan_id,
         len(clips_without_asset),
+        source_desc,
+        len(ready_videos),
+    )
+    random.shuffle(ready_videos)
+    for i, clip in enumerate(clips_without_asset):
+        asset = ready_videos[i % len(ready_videos)]
+        svc.assign_asset(clip.id, asset.id)
+    logger.info(
+        "模板编辑器自动兜底4: plan=%s 从 %s 分配了 %d 个素材给 %d 个片段",
+        plan_id,
+        source_desc,
+        len(ready_videos),
+        len(clips_without_asset),
     )
-    libs = asset_library_repo.find_by_project(plan_check.project_id)
-    video_lib = None
-    for lib in libs:
-        lib_kind = lib.kind.value if hasattr(lib.kind, "value") else lib.kind
-        if lib_kind == "video":
-            video_lib = lib
-            break
-
-    if video_lib:
-        assets = asset_repo.find_by_library(video_lib.id)
-        ready_videos = [
-            a
-            for a in assets
-            if (a.status.value if hasattr(a.status, "value") else a.status) == "ready"
-            and a.mime_type
-            and a.mime_type.startswith("video")
-        ]
-        if ready_videos:
-            random.shuffle(ready_videos)
-            for i, clip in enumerate(clips_without_asset):
-                asset = ready_videos[i % len(ready_videos)]
-                svc.assign_asset(clip.id, asset.id)
-            logger.info(
-                "模板编辑器自动兜底4: plan=%s 从素材库 %s 分配了 %d 个素材",
-                plan_id,
-                video_lib.name,
-                len(ready_videos),
-            )

apps/api/app/api/routes/templates_editor/generation.py

@@ -71,7 +71,8 @@ def generate_editor_draft(
     _auto_fallback_copy_template_clips(plan_svc, plan_id, plan_check, db)
     clips_without_asset = _auto_fallback_assign_assets(plan_svc, plan_id, plan_check)
     _auto_fallback_auto_material_mode(
-        plan_svc, plan_id, plan_check, clips_without_asset, asset_library_repo, asset_repo
+        plan_svc, plan_id, plan_check, clips_without_asset, asset_library_repo, asset_repo,
+        user_id=str(current_user.user.id),
     )
 
     # 检查是否可生成（含最后防线自动修复 + 诊断日志）

packages/adapters/sqlalchemy_impl/asset_repository.py

@@ -284,6 +284,24 @@ class SQLAlchemyAssetRepository:
         )
         return int(result or 0)
 
+    def find_ready_videos_by_user(
+        self,
+        user_id: str,
+        *,
+        limit: int = 50,
+    ) -> list[Asset]:
+        """查找用户上传的所有就绪视频素材。"""
+        query = self.session.query(AssetModel).filter(
+            AssetModel.uploaded_by_user_id == user_id,
+            AssetModel.status == "ready",
+            AssetModel.file_type == "video",
+        )
+        query = query.order_by(AssetModel.created_at.desc())
+        if limit > 0:
+            query = query.limit(limit)
+        models = query.all()
+        return [self._to_domain(m) for m in models]
+
     def search_candidates(
         self,
         project_id: str,