Fix Yjs WebSocket in dev mode

- Add Vite plugin implementing y-protocols sync server for dev mode
- Fix useYjs hook: move provider creation into useEffect to survive
  React StrictMode remounts
- Fix WebSocket URL: use /sync as base (y-websocket appends room name)
- Verified in browser: Connected status, Host badge, awareness working

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/planner/package.json

@@ -21,10 +21,12 @@
     "@trails-cool/ui": "workspace:*",
     "drizzle-orm": "catalog:",
     "isbot": "^5.1.0",
+    "lib0": "^0.2.117",
     "react": "catalog:",
     "react-dom": "catalog:",
     "react-router": "catalog:",
     "ws": "^8.20.0",
+    "y-protocols": "^1.0.7",
     "y-websocket": "^3.0.0",
     "yjs": "^13.6.30"
   },