Improve Docker healthcheck to validate schema initialization

- Check for 'users' table existence instead of just mysqladmin ping
- Ensures schema.sql has executed before marking as healthy
- Add 40s start_period for initial schema load
- Prevents Spring Boot from connecting to uninitialized database

docker-compose.dev.yml

@@ -15,10 +15,11 @@ services:
       - ./src/main/resources/schema.sql:/docker-entrypoint-initdb.d/01-schema.sql
       - ./src/main/resources/data.sql:/docker-entrypoint-initdb.d/02-data.sql
     healthcheck:
-      test: ["CMD", "mysqladmin", "ping", "-h", "127.0.0.1", "-uroot", "-proot"]
-      interval: 5s
+      test: ["CMD", "mysql", "-uroot", "-proot", "-e", "SELECT COUNT(*) FROM information_schema.tables WHERE table_schema='Petstoredb' AND table_name='users';"]
+      interval: 10s
       timeout: 5s
       retries: 30
+      start_period: 40s
 
 volumes:
   db_data: