fix(deployment): Redis health check reads password directly from Docker Secret

The health check now reads the password directly from /run/secrets/redis_password
instead of relying on an environment variable, which is not available in the
health check context.

This resolves the 'container application-redis-1 is unhealthy' error.

docker-compose.production.yml

@@ -209,9 +209,9 @@ services:
           cpus: '0.5'
 
     # Stricter health checks
-    # Uses REDIS_PASSWORD environment variable exported by entrypoint
+    # Health check reads password directly from Docker Secret
     healthcheck:
-      test: ["CMD-SHELL", "redis-cli -a \"$REDIS_PASSWORD\" ping | grep -q PONG"]
+      test: ["CMD-SHELL", "redis-cli -a \"$(cat /run/secrets/redis_password 2>/dev/null || echo '')\" ping | grep -q PONG"]
       interval: 10s
       timeout: 3s
       retries: 5