perf(*): bound list queries, batch fetches, harden media downloads

backend/src/userbot/runner.py

@@ -49,18 +49,6 @@ async def _cancel(task: asyncio.Task) -> None:
         await task
 
 
-async def _enqueue_once(pool: asyncpg.Pool, account_id: int, kind: str) -> None:
-    existing = await pool.fetchval(
-        "SELECT 1 FROM jobs WHERE account_id = $1 AND kind = $2 "
-        "AND status IN ('pending', 'running') LIMIT 1",
-        account_id,
-        kind,
-    )
-    if existing is None:
-        await enqueue(pool, account_id, kind, {})
-        logger.info(f"[green]Queued {kind}.[/]")
-
-
 class AccountRegistry:
     def __init__(self, pool: asyncpg.Pool, storage: ContentAddressedStorage) -> None:
         self._pool = pool
@@ -121,8 +109,8 @@ class AccountRegistry:
             client, asyncio.create_task(consumer.run()), device_model
         )
         logger.info(f"[green]Client started:[/] {me.full_name} ({me.id})")
-        await _enqueue_once(self._pool, account_id, "sync_dialogs")
-        await _enqueue_once(self._pool, account_id, "sync_contacts")
+        await enqueue(self._pool, account_id, "sync_dialogs", {})
+        await enqueue(self._pool, account_id, "sync_contacts", {})
 
     async def _stop(self, session_name: str) -> None:
         account = self._running.pop(session_name, None)