refactor: reorganize project structure and update configurations

- Move migrations/ to database/schema/ for clarity on database schema definitions
- Move sqlc.yaml to internal/database/ to group with database code
- Move static/ to cmd/server/static/ to co-locate with server
- Update all configuration files and documentation
- Follow Go project conventions for better organization

docker-compose.yml

@@ -10,7 +10,7 @@ services:
       POSTGRES_PASSWORD: ${DBPASS}
     volumes:
       - postgres_data:/var/lib/postgresql/data
-      - ./migrations:/docker-entrypoint-initdb.d
+      - ./database/schema:/docker-entrypoint-initdb.d
     ports:
       - "5432:5432"
     healthcheck: