Add env-var interpolation to docker-compose ports

[tp-abtion]

Allow unique host ports via POSTGRES_PORT/REDIS_PORT env vars with 5432/6379 defaults so multiple projects can run simultaneously.

Changes

• docker-compose.yml: Replace hardcoded ports with ${POSTGRES_PORT:-5432}:5432 and ${REDIS_PORT:-6379}:6379
• .env: Add POSTGRES_PORT=5432 and REDIS_PORT=6379 defaults
• README.md: Add "Custom Docker Ports" section

Impact

Zero impact for existing developers — defaults are unchanged.

[gemini-code-assist]

Code Review

This pull request introduces support for custom Docker ports for Postgres and Redis by adding environment variables to .env and updating the docker-compose.yml configuration. Documentation has been added to the README to explain this new capability. The review feedback identifies potential issues: the application's connection strings in .env remain hardcoded and should use variable expansion to stay in sync with the new port variables, the smtp4dev service ports should also be parameterized to prevent conflicts, and the documentation should explicitly clarify that changing ports requires corresponding updates to the application's connection strings.

[gemini-code-assist]

While adding these variables allows for Docker port customization, the connection strings DATABASE_SERVER (line 6) and REDIS_URL (line 13) still have hardcoded ports. If a developer changes the port variables, the application will fail to connect because it will still look for the services on the default ports. Consider using variable expansion within the .env file to keep them in sync, for example: DATABASE_SERVER=postgres://postgres:@127.0.0.1:${POSTGRES_PORT}.

[gemini-code-assist]

To fully support running multiple projects simultaneously as intended, the smtp4dev service ports (lines 20-21) should also be parameterized. Currently, they are hardcoded to 5000 and 2525, which will cause port conflicts if another instance of this template is running on the same host.

[gemini-code-assist]

It is important to clarify that changing these ports also requires updating the application's connection strings in the .env file, otherwise the app will not be able to reach the database or Redis.