feat: migrate e2e test infrastructure to @playwright/test

Replace direct playwright dependency with @playwright/test and add
playwright.config.js for centralized test configuration. Update run.sh
to invoke 'npx playwright test' instead of running test files with node.

tests/e2e/package.json

@@ -3,10 +3,10 @@
   "name": "porchlight-e2e",
   "description": "End-to-end browser tests for Porchlight",
   "scripts": {
-    "test": "./run.sh",
+    "test": "npx playwright test",
     "setup": "npx playwright install chromium"
   },
   "dependencies": {
-    "playwright": "^1.52.0"
+    "@playwright/test": "^1.52.0"
   }
 }