feat(P1): 素材列表支持按类型过滤 - 视频库/配音库分类

新增/修复:
- Asset domain 增加 file_type property（从 mime_type 推导）
- AssetRepository 新增 find_by_project_and_file_type / count_by_project_and_file_type / count_by_library_and_file_type
- 素材列表接口 kind 过滤全路径覆盖（DB层分页更高效）：
  - library_id模式：total改用count查询（之前用len(items)不准）
  - project_id模式：改用DB层file_type查询（之前内存过滤性能差）
  - 跨项目模式：新增kind过滤（之前完全没有）
  - 内存过滤路径：project_id和跨项目增加DB层预过滤+改用file_type判断
- 向后兼容：kind参数已存在，只是之前不完整

apps/api/app/api/routes/assets.py

@@ -201,7 +201,7 @@ def list_assets(
                 items = asset_repository.find_by_library_and_file_type(
                     library_id, ft, skip=skip, limit=limit, status=status_list
                 )
-                total = len(items)
+                total = asset_repository.count_by_library_and_file_type(library_id, ft, status=status_list)
             else:
                 items = asset_repository.find_by_library(library_id, skip=skip, limit=limit, status=status_list)
                 total = asset_repository.count_by_project(library.project_id, status=status_list)
@@ -216,11 +216,11 @@ def list_assets(
         if project_id:
             check_project_access(project_id, user_id, project_repository)
             if ft:
-                # 无直接方法，加载后按 file_type 过滤（仍比全量加载好）
-                all_items = asset_repository.find_by_project(project_id, status=status_list)
-                items = [i for i in all_items if i.mime_type and i.mime_type.startswith(ft)]
-                total = len(items)
-                paged = items[skip : skip + limit]
+                items = asset_repository.find_by_project_and_file_type(
+                    project_id, ft, skip=skip, limit=limit, status=status_list
+                )
+                total = asset_repository.count_by_project_and_file_type(project_id, ft, status=status_list)
+                paged = items
             else:
                 items = asset_repository.find_by_project(project_id, skip=skip, limit=limit, status=status_list)
                 total = asset_repository.count_by_project(project_id, status=status_list)
@@ -243,22 +243,43 @@ def list_assets(
         if not project_ids:
             return ListAssetsResponse(items=[], total=0, skip=skip, limit=limit)
 
-        total = asset_repository.count_by_project_ids(project_ids, status=status_list)
-        # 跨项目分页：逐项目累积直到凑够一页
-        paged_items: list = []
-        offset = skip
-        remaining = limit
-        for pid in project_ids:
-            proj_total = asset_repository.count_by_project(pid, status=status_list)
-            if offset >= proj_total:
-                offset -= proj_total
-                continue
-            proj_items = asset_repository.find_by_project(pid, skip=offset, limit=remaining, status=status_list)
-            paged_items.extend(proj_items)
-            remaining -= len(proj_items)
-            offset = 0
-            if remaining <= 0:
-                break
+        if ft:
+            # 有 kind 过滤：逐项目查 file_type，凑够一页
+            total = 0
+            paged_items: list = []
+            offset = skip
+            remaining = limit
+            for pid in project_ids:
+                proj_total = asset_repository.count_by_project_and_file_type(pid, ft, status=status_list)
+                total += proj_total
+                if offset >= proj_total:
+                    offset -= proj_total
+                    continue
+                proj_items = asset_repository.find_by_project_and_file_type(
+                    pid, ft, skip=offset, limit=remaining, status=status_list
+                )
+                paged_items.extend(proj_items)
+                remaining -= len(proj_items)
+                offset = 0
+                if remaining <= 0:
+                    break
+        else:
+            total = asset_repository.count_by_project_ids(project_ids, status=status_list)
+            # 跨项目分页：逐项目累积直到凑够一页
+            paged_items: list = []
+            offset = skip
+            remaining = limit
+            for pid in project_ids:
+                proj_total = asset_repository.count_by_project(pid, status=status_list)
+                if offset >= proj_total:
+                    offset -= proj_total
+                    continue
+                proj_items = asset_repository.find_by_project(pid, skip=offset, limit=remaining, status=status_list)
+                paged_items.extend(proj_items)
+                remaining -= len(proj_items)
+                offset = 0
+                if remaining <= 0:
+                    break
 
         return ListAssetsResponse(
             items=[_to_asset_response(item) for item in paged_items],
@@ -281,7 +302,14 @@ def list_assets(
             all_items = asset_repository.find_by_library(library_id, status=status_list)
     elif project_id:
         check_project_access(project_id, user_id, project_repository)
-        all_items = asset_repository.find_by_project(project_id, status=status_list)
+        if kind:
+            ft = kind_to_file_type.get(kind)
+            if ft:
+                all_items = asset_repository.find_by_project_and_file_type(project_id, ft, status=status_list)
+            else:
+                all_items = asset_repository.find_by_project(project_id, status=status_list)
+        else:
+            all_items = asset_repository.find_by_project(project_id, status=status_list)
     else:
         try:
             projects = project_repository.find_accessible_projects(user_id)
@@ -290,12 +318,18 @@ def list_assets(
             return ListAssetsResponse(items=[], total=0, skip=skip, limit=limit)
         all_items = []
         for proj in projects:
-            all_items.extend(asset_repository.find_by_project(proj.id, status=status_list))
+            if kind and kind_to_file_type.get(kind):
+                all_items.extend(
+                    asset_repository.find_by_project_and_file_type(proj.id, kind_to_file_type[kind], status=status_list)
+                )
+            else:
+                all_items.extend(asset_repository.find_by_project(proj.id, status=status_list))
 
     # 应用 kind 过滤（如果有）+ keyword/gender/style
     if kind:
         ft = kind_to_file_type.get(kind)
-        all_items = [i for i in all_items if i.mime_type and i.mime_type.startswith(ft or "")]
+        if ft:
+            all_items = [i for i in all_items if i.file_type == ft]
     filtered = _apply_memory_filters(all_items)
     total = len(filtered)
     paged = filtered[skip : skip + limit]