Summary

Fixes #7528 — /claim #7528

When deploying a Docker Compose file via GitHub App (dockercompose buildpack), database services are not detected and ServiceDatabase records are not created — meaning automated backups are unavailable. This works correctly for “Empty Docker Compose” and one-click services.

Root Cause

• Empty Docker Compose → Service model → serviceParser() → calls isDatabaseImage() → creates ServiceDatabase ✅
• GitHub App dockercompose → Application model → applicationParser() → calls isDatabaseImage() but never creates ServiceDatabase ❌

ServiceDatabase had a non-nullable service_id FK, making it impossible to associate with an Application.

Changes

1. Migration — Add nullable application_id to service_databases, make service_id nullable
2. ServiceDatabase model — New application() relation + helper methods for polymorphic parent access
3. Application model — New databases() relation
4. parsers.php / shared.php — Detect DB images in applicationParser() and create ServiceDatabase records
5. DatabaseBackupJob — Use polymorphic getters instead of direct service-> access
6. ScheduledDatabaseBackup — Handle both service and application paths
7. DeleteResourceJob — Clean up ServiceDatabase on Application deletion
8. Routes + Livewire + Blade — New backup management UI for Application resources

Testing

• Database images are detected via isDatabaseImage() (same logic as service parser)
• Backup scheduling uses existing DatabaseBackupJob infrastructure
• Backward compatible: existing Service-based backups unaffected