Implement Redis rate limiting middleware for spam endpoints (FRE-4507)

- Add ioredis dependency to API package
- Create Redis connection utility (apps/api/src/config/redis.ts)
- Create Redis-backed spam rate limit middleware with per-minute and daily limits
- Create spam classification routes (SMS, number reputation, call analysis, feedback)
- Register middleware and routes in API server
- Add 7 passing tests for rate limit enforcement
- Update vitest config with required env vars

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/config/redis.ts

@@ -0,0 +1,18 @@
+import { Redis } from 'ioredis';
+
+const redisHost = process.env.REDIS_HOST || 'localhost';
+const redisPort = parseInt(process.env.REDIS_PORT || '6379', 10);
+
+export const redis = new Redis({
+  host: redisHost,
+  port: redisPort,
+  retryStrategy: (times: number) => Math.min(times * 50, 2000),
+  lazyConnect: true,
+});
+
+export async function getRedisConnection(): Promise<Redis> {
+  if (redis.status === 'wait' || redis.status === 'connecting') {
+    await redis.connect();
+  }
+  return redis;
+}