refactor(templates): Remove app templates now served from flatrun/templates

[nfebe]

The application templates were moved to flatrun/templates and are fetched at runtime, but the directories still sit in agent/templates/, where the minio and static ones back test fixtures.

Checklist

• Move the templates the tests depend on into testdata/
• Delete the remaining app template directories from agent/templates/
• Point the affected tests at the testdata copies

Follow-up to #200.