Performance: RCON pooling, route caching, parallel status probe

Server:
- lib/cache.ts: tiny TTL memo for hot paths.
- lib/rcon.ts: pooled connection with 30s idle close and one-shot retry;
  was opening a fresh TCP per RCON call.
- /api/status: race protocol-ping + RCON with Promise.any (was sequential
  with 5s timeouts) and memo 3s; adds Cache-Control.
- /api/players: memo 10s, invalidated on mutations.
- /api/mods: getModDetails memo 10s (invalidated on install/remove) —
  eliminates per-request readdirSync/statSync/AdmZip parse.
- /api/analytics: reverse-scan JSONL to window cutoff (O(window) vs O(file))
  and memo 30s.
- /api/logs: memo 2s to throttle journalctl spawns during Live mode.

Client:
- StatusCard + ServerControls: staleTime 5s, both poll every 10s, dedup
  via shared query key.
- Analytics: staleTime 30s; memoize sparkline SVG paths.
- Modrinth search icons + mc-heads avatars: width/height + loading=lazy +
  decoding=async.
- next.config.ts: images.remotePatterns for future next/image migration,
  explicit compress=true.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/cache.ts

@@ -0,0 +1,29 @@
+type Entry<T> = { value: T; expires: number };
+
+const store = new Map<string, Entry<unknown>>();
+
+export function memo<T>(key: string, ttlMs: number, fn: () => T): T {
+  const now = Date.now();
+  const hit = store.get(key) as Entry<T> | undefined;
+  if (hit && hit.expires > now) return hit.value;
+  const value = fn();
+  store.set(key, { value, expires: now + ttlMs });
+  return value;
+}
+
+export async function memoAsync<T>(
+  key: string,
+  ttlMs: number,
+  fn: () => Promise<T>
+): Promise<T> {
+  const now = Date.now();
+  const hit = store.get(key) as Entry<T> | undefined;
+  if (hit && hit.expires > now) return hit.value;
+  const value = await fn();
+  store.set(key, { value, expires: now + ttlMs });
+  return value;
+}
+
+export function invalidate(prefix: string): void {
+  for (const k of store.keys()) if (k.startsWith(prefix)) store.delete(k);
+}