Add Celebright holiday-lights integration

Home Assistant custom integration for Celebright (CLC-03) holiday-lights
controllers, plus a standalone reference client. Local-only, reverse-engineered
from the device's WebSocket protocol — talks directly to the controller on the
LAN with no vendor cloud.

- select entity exposes the device's saved scenes plus an off option
- firmware-v2 protocol (savedScenes); getSystemState drives availability and
  the active scene, scene library fetched best-effort and cached
- WS connect/recv/send wrapped in asyncio timeouts so a silent device can't
  blow past HA's setup deadline
- config flow prompts for the controller IP; no credentials involved
- docs/PROTOCOL.md: full v2 WebSocket protocol and device behaviors

Migrated from the private dfritz/celebright with history dropped and internal
site references removed. MIT-licensed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01F6B8b3iYNv6QUftK2FDfYb

.gitignore

@@ -0,0 +1,38 @@
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+*.egg-info/
+dist/
+build/
+
+# Virtual Environment
+.venv/
+venv/
+ENV/
+env/
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+.DS_Store?
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.db
+
+# Project specific
+*.pcapng
+*.pcap
+
+# Claude
+.claude/