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

backend/src/api/routers/chats.py

@@ -10,6 +10,7 @@ from utils.policy import repository
 from utils.read import chats
 from utils.read.models import (
     DEFAULT_LIMIT,
+    MAX_LIMIT,
     ChatListItem,
     MessageVersionView,
     MessageView,
@@ -49,6 +50,14 @@ async def list_chats(
     )
 
 
+@router.get("/chats/batch")
+async def get_chats_batch(
+    pool: FromDishka[asyncpg.Pool], account_id: AccountId, ids: Annotated[str, Query()]
+) -> list[ChatListItem]:
+    parsed = [int(part) for part in ids.split(",") if part.strip()]
+    return await chats.get_chats(pool, account_id, parsed[:MAX_LIMIT])
+
+
 @router.get("/chats/{chat_id}")
 async def get_chat(
     pool: FromDishka[asyncpg.Pool], chat_id: int, account_id: AccountId