feat: implement horizontal scaling optimizations for authz service

- Add /health and /ready endpoints for load balancer health checks
- Replace in-memory JWT token cache with Redis for multi-replica support
- Reduce DB connection pool from 100 to 25 connections per replica
- Add distributed rate limiting (100 req/min + 20 burst) using Redis
- Implement circuit breakers for DB and Redis to prevent cascading failures

This enables the service to scale horizontally with multiple replicas
behind a load balancer without exhausting database connections or
maintaining separate token caches per instance.

routes/routes.go

@@ -10,8 +10,16 @@ import (
 )
 
 func SetupRoutes(router *mux.Router, db *sql.DB) {
+	// Health check endpoints (no auth required)
+	router.HandleFunc("/health", handlers.HealthHandler).Methods("GET")
+	router.HandleFunc("/ready", handlers.ReadyHandler).Methods("GET")
+
+	// Rate limit configuration
+	rateLimitConfig := middleware.DefaultRateLimitConfig()
+	rateLimiter := middleware.RateLimiterMiddleware(rateLimitConfig)
+
 	authRoutes := router.PathPrefix("/v1/auth").Subrouter()
-	authRoutes.HandleFunc("/check", middleware.JWTAuth(handlers.AuthorizeHandler)).Methods("POST")
+	authRoutes.HandleFunc("/check", rateLimiter(middleware.JWTAuth(handlers.AuthorizeHandler))).Methods("POST")
 
 	router.PathPrefix("/swagger/").Handler(httpSwagger.WrapHandler)
 }