feat(api,userbot,frontend): search peers without chats and start tracking them

frontend/src/lib/stores/discover.svelte.ts

@@ -0,0 +1,41 @@
+import { getDiscoverItem } from "$lib/api/endpoints";
+import type { DiscoverItem } from "$lib/api/types";
+import { accounts } from "$lib/stores/accounts.svelte";
+
+function createDiscover() {
+  let items = $state<Record<number, DiscoverItem>>({});
+  let account: number | null = null;
+  const pending = new Set<number>();
+
+  function syncAccount() {
+    if (accounts.selectedId !== account) {
+      account = accounts.selectedId;
+      items = {};
+      pending.clear();
+    }
+  }
+
+  return {
+    get(chatId: number): DiscoverItem | undefined {
+      return items[chatId];
+    },
+    set(item: DiscoverItem) {
+      items = { ...items, [item.chat_id]: item };
+    },
+    async ensure(chatId: number) {
+      syncAccount();
+      if (account === null || items[chatId] || pending.has(chatId)) {
+        return;
+      }
+      pending.add(chatId);
+      try {
+        const item = await getDiscoverItem(chatId);
+        items = { ...items, [chatId]: item };
+      } finally {
+        pending.delete(chatId);
+      }
+    },
+  };
+}
+
+export const discover = createDiscover();