Fix Vitest browser provider setup and test cleanup

- Add @vitest/browser-playwright; use playwright() factory (not string)
- Import page from vitest/browser (not deprecated @vitest/browser/context)
- Add afterEach(cleanup) so each test gets a fresh DOM
- Use oxc transform for JSX instead of esbuild (avoids Vite 8 warning)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/planner/package.json

@@ -55,6 +55,7 @@
     "@types/react-dom": "catalog:",
     "@types/ws": "^8.18.1",
     "@vitest/browser": "^4.1.5",
+    "@vitest/browser-playwright": "^4.1.5",
     "leaflet.markercluster": "^1.5.3",
     "pino-pretty": "^13.1.3",
     "tailwindcss": "catalog:",