Pin Tracker Docker image to v4.0.0 after release

[josecelano]

Overview

Update the Tracker Docker image tag from develop to v4.0.0 once Tracker version 4.0.0 is released.

File: templates/docker-compose/docker-compose.yml.tera
Current: torrust/tracker:develop
Target: torrust/tracker:v4.0.0

Rationale

The develop tag is not a good choice for production deployments because:

• ❌ Breaking changes risk: The develop tag can introduce breaking changes at any time
• ❌ Compatibility issues: We need to ensure all services in the compose stack are compatible
• ✅ Manual verification: Image version changes must be introduced manually after verifying the new combination of versions works correctly

Implementation

Wait for release: This issue should be implemented after Tracker v4.0.0 is officially released.

Steps:

1. Wait for Tracker v4.0.0 release announcement
2. Update templates/docker-compose/docker-compose.yml.tera line 24:

   # Change from:
   image: torrust/tracker:develop
   # To:
   image: torrust/tracker:v4.0.0

3. Run E2E tests to verify compatibility with current Prometheus, Grafana, and MySQL versions
4. Verify all services start correctly and health checks pass
5. Verify Tracker metrics are scraped by Prometheus
6. Update any related documentation if needed

Acceptance Criteria

• Docker image tag changed from develop to v4.0.0
• Pre-commit checks pass: ./scripts/pre-commit.sh
• E2E tests pass with the updated image
• All service health checks pass (Tracker, Prometheus, Grafana, MySQL)
• Tracker metrics endpoint is accessible
• Prometheus successfully scrapes Tracker metrics

Related

• Parent: Update Docker Images to Latest Stable Versions #253 (Update Docker Images to Latest Stable Versions) - Phase 0 mentioned this as follow-up task
• Tracker Repository: https://github.com/torrust/torrust-tracker