feat: 文件夹批量处理引擎（后端）

- BatchWorker 单线程轮询 batch_jobs 表，处理 source=batch 的运行，
  与主调度器互不抢占（next_queued_run 排除 batch 来源）
- 直接读取用户所选文件夹下的视频逐个执行流水线，不上传到工作目录；
  中间态与产物落在视频旁同名文件夹，batch.done.json 完成标记去重
- 支持暂停/继续、失败容错（单视频失败不阻塞后续）、删除任务只清库
- 孤儿清理跳过 source=batch 运行，防止误删用户视频文件夹
- workflow_runs 新增 source 列（upload/batch），旧库自动迁移

tests/test_db.py

@@ -329,3 +329,103 @@ def test_restore_run_outputs(tmp_path) -> None:
         "extract": {"frames_manifest": "frames.json"}
     }
     assert db.restore_run_outputs("run_none") == {}
+
+
+def test_run_source_column_default_and_next_queued(tmp_path) -> None:
+    """source 列默认 upload；主调度器不拾取 batch 来源的运行。"""
+    db = Database(tmp_path / "wov.db")
+    db.upsert_workflow({"id": "demo", "name": "Demo", "published": 1, "latest_version": 1})
+    now = "2026-01-01T00:00:00+00:00"
+    db.create_run(
+        {
+            "id": "run_upload",
+            "workflow_id": "demo",
+            "workflow_version": 1,
+            "status": "QUEUED",
+            "progress": 0,
+            "created_at": now,
+            "updated_at": now,
+        }
+    )
+    db.create_run(
+        {
+            "id": "run_batch",
+            "workflow_id": "demo",
+            "workflow_version": 1,
+            "status": "QUEUED",
+            "progress": 0,
+            "source": "batch",
+            "created_at": now,
+            "updated_at": now,
+        }
+    )
+    # 默认 source 为 upload，可显式指定 batch。
+    assert db.get_run("run_upload")["source"] == "upload"
+    assert db.get_run("run_batch")["source"] == "batch"
+    # 主调度器只取非 batch 运行，批量运行由批量引擎单独拾起。
+    assert db.next_queued_run()["id"] == "run_upload"
+
+
+def test_db_migration_adds_source_column(tmp_path) -> None:
+    """旧库迁移：缺少 source 列的库打开后自动补列并默认 upload。"""
+    import sqlite3
+
+    db_path = tmp_path / "old.db"
+    conn = sqlite3.connect(db_path)
+    conn.execute(
+        "CREATE TABLE workflow_runs (id TEXT PRIMARY KEY, workflow_id TEXT NOT NULL,"
+        " workflow_version INTEGER NOT NULL, status TEXT NOT NULL, current_node_id TEXT,"
+        " progress REAL NOT NULL DEFAULT 0, error TEXT, input_uri TEXT,"
+        " param_overrides TEXT, created_at TEXT NOT NULL, updated_at TEXT NOT NULL)"
+    )
+    conn.commit()
+    conn.close()
+
+    Database(db_path)
+    conn = sqlite3.connect(db_path)
+    columns = [row[1] for row in conn.execute("PRAGMA table_info(workflow_runs)")]
+    conn.close()
+    assert "source" in columns
+
+
+def test_batch_jobs_and_videos_crud(tmp_path) -> None:
+    """批量任务/视频明细的增删改查与排队查询。"""
+    db = Database(tmp_path / "wov.db")
+    now = "2026-01-01T00:00:00+00:00"
+    db.create_batch_job(
+        {
+            "id": "batch_1", "folder_path": "/videos", "workflow_id": "demo",
+            "recursive": 1, "status": "QUEUED", "progress": 0, "total": 2,
+            "done": 0, "failed": 0, "current_video": None, "error": None,
+            "created_at": now, "updated_at": now,
+        }
+    )
+    assert db.next_queued_batch_job()["id"] == "batch_1"
+    assert db.list_batch_job_ids() == ["batch_1"]
+    assert db.list_batch_jobs()[0]["total"] == 2
+
+    db.create_batch_video(
+        {
+            "id": "bv_1", "job_id": "batch_1", "video_path": "/videos/a.mp4",
+            "work_dir": "/videos/a", "run_id": None, "status": "PENDING",
+            "error": None, "created_at": now, "updated_at": now,
+        }
+    )
+    db.update_batch_video("bv_1", status="COMPLETED", updated_at=now)
+    assert db.get_batch_video("bv_1")["status"] == "COMPLETED"
+    assert len(db.list_batch_videos("batch_1")) == 1
+
+    # 未知字段更新被忽略（不会报错也不会改状态）。
+    db.update_batch_video("bv_1", bogus=1, updated_at=now)
+    db.update_batch_job("batch_1", bogus=1, updated_at=now)
+    assert db.get_batch_video("bv_1")["status"] == "COMPLETED"
+
+    db.update_batch_job("batch_1", status="COMPLETED", done=1, failed=0, progress=1.0, updated_at=now)
+    job = db.get_batch_job("batch_1")
+    assert job["status"] == "COMPLETED" and job["done"] == 1
+    # 完成后不再排队。
+    assert db.next_queued_batch_job() is None
+
+    db.delete_batch_job("batch_1")
+    assert db.get_batch_job("batch_1") is None
+    assert db.get_batch_video("bv_1") is None