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/auth-precheck.ts

@@ -19,7 +19,7 @@ export async function precheckLogin(
   const p = String(password ?? "");
   if (!u || !p) return "invalid";
 
-  if (!rateLimit(`precheck:${await clientIp()}`, 10, 5 * 60_000).ok) return "invalid";
+  if (!(await rateLimit(`precheck:${await clientIp()}`, 10, 5 * 60_000)).ok) return "invalid";
 
   let user: { password: string; twoFactorConfirmedAt: Date | null } | null = null;
   try {