fix(sqlite): avoid validation database locked under high concurrency

- Release DB connection during validator.validate(); serialize writes with asyncio.Lock
- Add busy_timeout and longer connect timeout on aiosqlite connections
- WAL writes no longer contend across 120 parallel workers holding long-lived connections

Made-with: Cursor

app/core/db.py

@@ -16,12 +16,21 @@ def ensure_db_dir():
         os.makedirs(db_dir, exist_ok=True)
 
 
+async def _apply_connection_pragmas(db: aiosqlite.Connection) -> None:
+    await db.execute("PRAGMA journal_mode=WAL")
+    await db.execute("PRAGMA synchronous=NORMAL")
+    await db.execute("PRAGMA busy_timeout=30000")
+
+
+# aiosqlite/sqlite3：等待锁的最长时间（秒），与高并发验证写入配合
+_SQLITE_CONNECT_TIMEOUT = 30.0
+
+
 async def init_db():
     """初始化数据库表结构（支持迁移）"""
     ensure_db_dir()
-    async with aiosqlite.connect(DB_PATH) as db:
-        await db.execute("PRAGMA journal_mode=WAL")
-        await db.execute("PRAGMA synchronous=NORMAL")
+    async with aiosqlite.connect(DB_PATH, timeout=_SQLITE_CONNECT_TIMEOUT) as db:
+        await _apply_connection_pragmas(db)
         await db.execute("PRAGMA cache_size=-64000")
         await db.execute("PRAGMA temp_store=MEMORY")
 
@@ -120,10 +129,9 @@ async def init_db():
 async def get_db() -> AsyncIterator[aiosqlite.Connection]:
     """获取数据库连接的异步上下文管理器"""
     ensure_db_dir()
-    db = await aiosqlite.connect(DB_PATH)
+    db = await aiosqlite.connect(DB_PATH, timeout=_SQLITE_CONNECT_TIMEOUT)
     try:
-        await db.execute("PRAGMA journal_mode=WAL")
-        await db.execute("PRAGMA synchronous=NORMAL")
+        await _apply_connection_pragmas(db)
         yield db
     finally:
         await db.close()
@@ -131,12 +139,11 @@ async def get_db() -> AsyncIterator[aiosqlite.Connection]:
 
 @asynccontextmanager
 async def get_db_connection() -> AsyncIterator[aiosqlite.Connection]:
-    """单连接贯穿「读库 → await 网络 I/O → 写库」，减少验证 worker 每条代理两次 connect。"""
+    """与 get_db 相同 pragma/超时；保留别名供需「长连接」语义处使用。"""
     ensure_db_dir()
-    db = await aiosqlite.connect(DB_PATH)
+    db = await aiosqlite.connect(DB_PATH, timeout=_SQLITE_CONNECT_TIMEOUT)
     try:
-        await db.execute("PRAGMA journal_mode=WAL")
-        await db.execute("PRAGMA synchronous=NORMAL")
+        await _apply_connection_pragmas(db)
         yield db
     finally:
         await db.close()
@@ -152,10 +159,9 @@ async def transaction() -> AsyncIterator[aiosqlite.Connection]:
             # 如果抛出异常，自动 rollback
     """
     ensure_db_dir()
-    db = await aiosqlite.connect(DB_PATH)
+    db = await aiosqlite.connect(DB_PATH, timeout=_SQLITE_CONNECT_TIMEOUT)
     try:
-        await db.execute("PRAGMA journal_mode=WAL")
-        await db.execute("PRAGMA synchronous=NORMAL")
+        await _apply_connection_pragmas(db)
         await db.execute("BEGIN")
         yield db
         await db.commit()