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

frontend/src/lib/components/stories/AllStoriesArchive.svelte

@@ -2,7 +2,7 @@
   import { untrack } from "svelte";
   import {
     enqueueStoriesBackfill,
-    getChat,
+    getChatsBatch,
     getPeers,
     getStories,
   } from "$lib/api/endpoints";
@@ -63,17 +63,13 @@
       const chatIds = [...byPeer.keys()].filter((id) => id < 0);
       const [peers, fetched] = await Promise.all([
         getPeers(peerIds),
-        Promise.all(chatIds.map((id) => getChat(id))),
+        getChatsBatch(chatIds),
       ]);
       if (current !== token) {
         return;
       }
       const peerById = new Map(peers.map((peer) => [peer.peer_id, peer]));
-      const chatById = new Map(
-        fetched
-          .filter((item) => item !== null)
-          .map((item) => [item.chat_id, item])
-      );
+      const chatById = new Map(fetched.map((item) => [item.chat_id, item]));
       groups = [...byPeer.entries()].map(([peerId, stories]) => {
         if (peerId > 0) {
           const peer = peerById.get(peerId) ?? null;