v0.21.1: Add GET /api/config endpoint for live config content

New endpoint returns raw controller.yaml content (text/yaml) for Hub
live diff and pull operations. Same auth as other config endpoints.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/README.md

@@ -1066,6 +1066,7 @@ Self-update endpoints accept session auth OR `Authorization: Bearer <hub_api_key
 |--------|----------|-------------|
 | POST | `/api/config/apply` | Apply new controller.yaml from Hub (atomic write) |
 | GET | `/api/config/hash` | Get SHA256 hash of current controller.yaml |
+| GET | `/api/config` | Get raw controller.yaml content (text/yaml) for live diff and pull |
 
 Config endpoints accept session auth OR `Authorization: Bearer <hub_api_key>` (same as self-update). The `/api/config/apply` endpoint:
 - Accepts raw YAML body (the generated config from Hub)
@@ -1162,6 +1163,7 @@ See `docker-compose.yml` for the full volume configuration.
 - [x] Disaster recovery (v0.15.5) — Hub-based infra backup, auto-mount by UUID, restore UI with full-page takeover
 - [x] Controller self-update (v0.16.0) — Watchtower-style pull + restart, Settings page UI, API key auth, auto-update scheduling
 - [x] Hub-managed config (v0.20.0) — Config apply endpoint (`POST /api/config/apply`), config hash in reports for sync comparison
+- [x] Config content endpoint (v0.21.1) — `GET /api/config` returns raw YAML for Hub live diff and pull operations
 
 ### In Progress / Planned