chore: clean up repo structure

- Add node_modules/, test-results/, e2e-report/, .omp/ to .gitignore
- Remove throwaway debug scripts (debug-pw*.js, debug-login-dom.js)
- Remove empty mock-server/ directory
- Untrack harness artifact (.omp/plans/)
- Add missing project files to git (e2e tests, Dockerfiles, tooling configs)

package.json

@@ -0,0 +1,15 @@
+{
+  "name": "luci-app-zt-gateway-e2e",
+  "version": "1.0.0",
+  "private": true,
+  "devDependencies": {
+    "@playwright/test": "^1.58.1"
+  },
+  "scripts": {
+    "test:e2e": "playwright test",
+    "test:e2e:ui": "playwright test --ui",
+    "test:e2e:headed": "playwright test --headed",
+    "test:e2e:debug": "playwright test --debug",
+    "test:e2e:report": "npx playwright show-report"
+  }
+}