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/package.json

@@ -16,7 +16,8 @@
     "@shieldsai/shared-notifications": "*",
     "@shieldsai/shared-utils": "*",
     "fastify": "^4.25.0",
-    "fastify-plugin": "^4.5.0"
+    "fastify-plugin": "^4.5.0",
+    "ioredis": "^5.3.0"
   },
   "devDependencies": {
     "@types/node": "^25.6.0",