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

frontend/src/lib/api/media.ts

@@ -102,9 +102,30 @@ export function visualKind(kind: string): VisualKind {
   return "other";
 }
 
+const MAX_CACHED = 200;
+
 const ready = new Map<string, InlineMedia>();
 const inflight = new Map<string, Promise<InlineMedia>>();
 
+function remember(
+  cache: Map<string, InlineMedia>,
+  key: string,
+  item: InlineMedia
+) {
+  cache.set(key, item);
+  while (cache.size > MAX_CACHED) {
+    const oldest = cache.keys().next();
+    if (oldest.done) {
+      return;
+    }
+    const stale = cache.get(oldest.value);
+    cache.delete(oldest.value);
+    if (stale?.state === "ready") {
+      URL.revokeObjectURL(stale.url);
+    }
+  }
+}
+
 function cacheKey(account: number, chatId: number, messageId: number): string {
   return `${account}:${chatId}:${messageId}`;
 }
@@ -183,7 +204,7 @@ export function loadMediaItem(media: MediaRef): Promise<InlineMedia> {
   const promise = resolveById(media)
     .then((result) => {
       if (result.state === "ready") {
-        byId.set(key, result);
+        remember(byId, key, result);
       }
       return result;
     })
@@ -251,7 +272,7 @@ export function loadInlineMedia(
   const promise = resolve(chatId, messageId)
     .then((result) => {
       if (result.state === "ready") {
-        ready.set(key, result);
+        remember(ready, key, result);
       }
       return result;
     })