feat(video-lab): app/db.py — video_tasks 테이블 + CRUD (SP-8)

WAL + busy_timeout 표준 fix. create_task / update_task / get_task.
provider 컬럼 추가(Sora/Veo/Kling/Seedance 구분). video_url 필드.
Plan-B-Video Phase 1.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

video-lab/app/db.py

@@ -0,0 +1,95 @@
+"""SQLite persistence for video_tasks. Single table — task 단위 추적만."""
+from __future__ import annotations
+
+import json
+import os
+import sqlite3
+from contextlib import contextmanager
+from typing import Any, Dict, Optional
+
+DB_PATH = os.path.join(os.getenv("VIDEO_DATA_DIR", "/app/data"), "video.db")
+
+
+@contextmanager
+def _conn():
+    os.makedirs(os.path.dirname(DB_PATH), exist_ok=True)
+    conn = sqlite3.connect(DB_PATH)
+    conn.row_factory = sqlite3.Row
+    conn.execute("PRAGMA journal_mode=WAL")
+    conn.execute("PRAGMA busy_timeout=5000")
+    try:
+        yield conn
+        conn.commit()
+    finally:
+        conn.close()
+
+
+def init_db() -> None:
+    with _conn() as conn:
+        conn.execute(
+            """
+            CREATE TABLE IF NOT EXISTS video_tasks (
+                id          TEXT PRIMARY KEY,
+                provider    TEXT NOT NULL,
+                params      TEXT NOT NULL,
+                status      TEXT DEFAULT 'queued',
+                progress    INTEGER DEFAULT 0,
+                message     TEXT DEFAULT '',
+                video_url   TEXT,
+                error       TEXT,
+                created_at  TEXT DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now')),
+                updated_at  TEXT DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now'))
+            )
+            """
+        )
+
+
+def _row_to_dict(row) -> Dict[str, Any]:
+    return {
+        "id": row["id"],
+        "provider": row["provider"],
+        "params": row["params"],
+        "status": row["status"],
+        "progress": row["progress"],
+        "message": row["message"],
+        "video_url": row["video_url"],
+        "error": row["error"],
+        "created_at": row["created_at"],
+        "updated_at": row["updated_at"],
+    }
+
+
+def create_task(task_id: str, provider: str, params: Dict[str, Any]) -> Dict[str, Any]:
+    with _conn() as conn:
+        conn.execute(
+            "INSERT INTO video_tasks (id, provider, params) VALUES (?, ?, ?)",
+            (task_id, provider, json.dumps(params)),
+        )
+        row = conn.execute("SELECT * FROM video_tasks WHERE id = ?", (task_id,)).fetchone()
+    return _row_to_dict(row)
+
+
+def update_task(
+    task_id: str,
+    status: str,
+    progress: int,
+    message: str = "",
+    video_url: Optional[str] = None,
+    error: Optional[str] = None,
+) -> None:
+    with _conn() as conn:
+        conn.execute(
+            """
+            UPDATE video_tasks
+            SET status = ?, progress = ?, message = ?, video_url = ?, error = ?,
+                updated_at = strftime('%Y-%m-%dT%H:%M:%fZ','now')
+            WHERE id = ?
+            """,
+            (status, progress, message, video_url, error, task_id),
+        )
+
+
+def get_task(task_id: str) -> Optional[Dict[str, Any]]:
+    with _conn() as conn:
+        row = conn.execute("SELECT * FROM video_tasks WHERE id = ?", (task_id,)).fetchone()
+    return _row_to_dict(row) if row else None