fix: FediDB instance search now filters by query

The FediDB /v1/servers API ignores the q parameter and always returns
the same top-10 ranked list. Changed to fetch the full 40-server list
once (cached 24h) and filter server-side by domain/software match.

lib/fedidb.js

@@ -71,26 +71,21 @@ async function writeToCache(kvCollection, cacheKey, data) {
 }
 
 /**
- * Search FediDB for instances matching a query.
- * Returns a flat array of { domain, software, description, mau, openRegistration }.
- *
- * Results are cached per normalized query for 24 hours.
+ * Get the full FediDB server list (up to 40, the API max).
+ * Cached for 24 hours as a single entry. The API ignores query params
+ * and always returns the same ranked-by-MAU list, so we fetch once
+ * and filter client-side in searchInstances().
  *
  * @param {object} kvCollection - MongoDB ap_kv collection
- * @param {string} query - Search term (e.g. "mast")
- * @param {number} [limit=10] - Max results
  * @returns {Promise<Array>}
  */
-export async function searchInstances(kvCollection, query, limit = 10) {
-  const q = (query || "").trim().toLowerCase();
-  if (!q) return [];
-
-  const cacheKey = `fedidb:instances:${q}:${limit}`;
+async function getAllServers(kvCollection) {
+  const cacheKey = "fedidb:servers-all";
   const cached = await getFromCache(kvCollection, cacheKey);
   if (cached) return cached;
 
   try {
-    const url = `${API_BASE}/servers?q=${encodeURIComponent(q)}&limit=${limit}`;
+    const url = `${API_BASE}/servers?limit=40`;
     const res = await fetchWithTimeout(url);
     if (!res.ok) return [];
 
@@ -113,6 +108,34 @@ export async function searchInstances(kvCollection, query, limit = 10) {
   }
 }
 
+/**
+ * Search FediDB for instances matching a query.
+ * Returns a flat array of { domain, software, description, mau, openRegistration }.
+ *
+ * Fetches the full server list once (cached 24h) and filters by domain/software match.
+ * FediDB's /v1/servers endpoint ignores the `q` param and always returns a static
+ * ranked list, so server-side filtering is the only way to get relevant results.
+ *
+ * @param {object} kvCollection - MongoDB ap_kv collection
+ * @param {string} query - Search term (e.g. "mast")
+ * @param {number} [limit=10] - Max results
+ * @returns {Promise<Array>}
+ */
+export async function searchInstances(kvCollection, query, limit = 10) {
+  const q = (query || "").trim().toLowerCase();
+  if (!q) return [];
+
+  const allServers = await getAllServers(kvCollection);
+
+  return allServers
+    .filter(
+      (s) =>
+        s.domain.toLowerCase().includes(q) ||
+        s.software.toLowerCase().includes(q),
+    )
+    .slice(0, limit);
+}
+
 /**
  * Check if a remote instance supports unauthenticated public timeline access.
  * Makes a lightweight HEAD-like request (limit=1) to the Mastodon public timeline API.