fix: browser testing issues and missing UI tools

- Fix WebSocket URL to use ws:// for http development environments
- Make createLayer idempotent to prevent race-condition 500 under React StrictMode
- Add URL-based routing for /register so register page actually shows register form
- Add missing tool buttons to LeftSidebar: polygon, chair, extend, fillet
- Add Playwright browser test suite for exhaustive UI testing
- Update .gitignore for Playwright artifacts

Unit tests: backend 254/254, frontend 380/380

frontend/src/crdt/useYjsBinding.ts

@@ -57,7 +57,7 @@ export interface UseYjsBindingResult {
   clearSelection: () => void;
 }
 
-const DEFAULT_WS_URL = `wss://${window.location.host}`;
+const DEFAULT_WS_URL = `${window.location.protocol === 'https:' ? 'wss' : 'ws'}://${window.location.host}`;
 
 export function useYjsBinding(opts: UseYjsBindingOptions): UseYjsBindingResult {
   const { docName, wsUrl = DEFAULT_WS_URL, userId, userName, userColor, enabled = true, token } = opts;