fix: remove port expose on db

[kurokobo]

Summary

Closes #15285

In the PR #13836 that introduced the plugin feature, the ports was added to the db in the docker-compose.yml, allowing PostgreSQL to be exposed outside the Docker host by default.

This configuration is unnecessary for typical self-hosting scenarios.

It simply increases the potential for unauthorized access to the database and attacks. Due to the high security risk, the any port should be kept private by default.

Screenshots

Before	After

Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods