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

contexts/frontend.md

@@ -4,7 +4,7 @@
 
 ## CSS Custom Properties (Variables)
 
-Defined in `server/src/wled_controller/static/css/base.css`.
+Defined in `server/src/ledgrab/static/css/base.css`.
 
 **IMPORTANT:** There is NO `--accent` variable. Always use `--primary-color` for accent/brand color.