perf: add bans.user_id index, Redis cache layer, rate-limit improvements, radio contest/giveaway columns, and tests

- Add DB index on bans.user_id to speed up per-request ban lookups (migration 0008)
- Replace in-process rate limiter with Redis-backed implementation with in-memory fallback
- Add Redis caching layer for site settings with TTL invalidation (migration 0009)
- Add rate limiting to resetPassword to prevent token brute-force attacks
- Update all rateLimit callers to await the now-async function
- Flesh out RadioContests and RadioGiveaways models with title, description, prize, date, and winner columns
- Update radio contest/giveaway pages to display new fields
- Add tests for rate limiter (4 tests) and password-reset actions (3 tests)
- Add REDIS_URL environment variable (optional, falls back to in-memory)

src/actions/help-tickets.ts

@@ -19,7 +19,7 @@ export async function createTicket(formData: FormData): Promise<void> {
   if (!Number.isInteger(userId) || userId <= 0) return;
 
   const ip = await clientIp();
-  if (!rateLimit(`ticket:${userId}`, 3, 60_000).ok) return;
+  if (!(await rateLimit(`ticket:${userId}`, 3, 60_000)).ok) return;
 
   const raw = {
     title: String(formData.get("title") ?? "").trim().slice(0, 255),