refactor: rename project to LedGrab, split HA integration into separate repo

- Rename Python package: wled_controller -> ledgrab
- Rename env var prefix: WLED_ -> LEDGRAB_ (with auto-migration for old vars)
- Rename localStorage key: wled_api_key -> ledgrab_api_key (with migration)
- Rename HA integration domain: wled_screen_controller -> ledgrab
- Update all imports, build scripts, Docker, installer, config, docs
- Remove HA integration (moved to ledgrab-haos-integration repo)
- Remove hacs.json (belongs in HA repo now)
- Add startup warning for users with old WLED_ env vars
- All tests pass (715/715), ruff clean, tsc clean, frontend builds

docs/API.md

@@ -1,6 +1,6 @@
-# WLED Screen Controller API Documentation
+# LedGrab API Documentation
 
-Complete REST API reference for the WLED Screen Controller server.
+Complete REST API reference for the LedGrab server.
 
 **Base URL:** `http://localhost:8080`
 **API Version:** v1