Add JSON REST API for MCP integration

- Add /api/v1 namespace with Bearer token auth (PINCHFLAT_API_TOKEN env var)
- API controllers for sources, media items, media profiles, settings, tasks
- Support for all source actions: create, update, delete, force_download_pending,
  force_redownload, force_index, force_metadata_refresh, sync_files_on_disk
- Media item endpoints: list, show, search, force_download, update, delete
- Media profile CRUD endpoints
- Settings show/update and app_info endpoints
- Task listing endpoints
- Add Jason.Encoder for Task schema
- Comprehensive test suite for all API endpoints
- Gitea Actions CI workflow (runs existing checks + API-specific tests)
- API documentation in docs/API.md

config/test.exs

@@ -11,6 +11,10 @@ config :pinchflat,
 
 config :pinchflat, Oban, testing: :manual
 
+# API token is not set in tests by default — allows tests to run without auth.
+# Individual tests that need auth can set it via Application.put_env.
+config :pinchflat, :api_token, nil
+
 # Configure your database
 #
 # The MIX_TEST_PARTITION environment variable can be used