feat(services): add TREK travel planner one-click service template

[YAlmuzaini]

Changes

Adds TREK as a one-click service template. Resubmission of #9213, addressing all feedback from @ShadowArcanist:

• Pinned image to 2.7.2 instead of latest
• Removed restart policy (handled by Coolify)
• Added ENCRYPTION_KEY via SERVICE_PASSWORD_64_ENCRYPTIONKEY
• Using /api/health for healthchecks
• FORCE_HTTPS defaults to false (Traefik handles TLS)
• Admin credentials shown on dashboard via ADMIN_EMAIL and SERVICE_PASSWORD_ADMIN
• Includes OIDC/SSO env vars
• Named volumes for /app/data and /app/uploads

TREK is a self-hosted collaborative travel planner (~3k stars, AGPL-3.0).

Issues

• Resubmission of feat(services): add NOMAD travel planner service template #9213

Category

• Bug fix
• Improvement
• New feature
• Adding new one click service
• Fixing or updating existing one click service

Preview

AI Assistance

• AI was NOT used to create this PR
• AI was used (please describe below)

If AI was used:

• Tools used: Claude Code
• How extensively: Used to research existing template patterns and identify correct Coolify magic variables. All changes reviewed and tested manually.

Testing

• Deployed via Coolify one-click service
• Container starts and healthcheck passes (/api/health)
• App accessible via generated URL
• Admin credentials visible on Coolify dashboard
• Data persists across restarts

Contributor Agreement

Important

• I have read and understood the contributor guidelines. If I have failed to follow any guideline, I understand that this PR may be closed without review.
• I have searched existing issues and pull requests (including closed ones) to ensure this isn't a duplicate.
• I have tested all the changes thoroughly with a local development instance of Coolify and I am confident that they will work as expected when a maintainer tests them.