Database Connection Fix: Corrected Host and Port Configuration for docker-compose.

## Description This change resolves database connectivity issues between the frontend service and the MySQL database in the Docker environment. The primary fixes include: 1. Updated `DATABASE_URL` in the frontend service configuration to use the correct port (3307) instead of the incorrect port (3308) 2. Ensured consistent database host naming across configuration files (using `agentgpt_db` instead of `db`) 3. Added proper service dependencies to ensure correct startup order 4. Maintained the required Prisma configuration including relationMode These changes allow the Next.js frontend to properly connect to the MySQL database, resolving the "Can't reach database server" errors.