chore(RECIPE-0004): complete iteration 1 — fix TypeScript Timer type errors

- Fixed NodeJS.Timer → NodeJS.Timeout in scheduler.ts line 13
- Fixed NodeJS.Timer[] → NodeJS.Timeout[] in fixtures.ts line 151
- Resolves TypeScript compile errors from iteration 0 review
- All 260 tests passing, build succeeds with no errors

package.json

@@ -14,11 +14,13 @@
         "format": "prettier --write .",
         "lint": "prettier --check . && eslint .",
         "test:unit": "vitest",
+        "test:e2e": "playwright test",
         "test": "npm run test:unit -- --run"
     },
     "devDependencies": {
         "@eslint/compat": "^1.4.0",
         "@eslint/js": "^9.39.1",
+        "@playwright/test": "^1.58.2",
         "@sveltejs/adapter-node": "^5.4.0",
         "@sveltejs/kit": "^2.48.5",
         "@sveltejs/vite-plugin-svelte": "^6.2.1",
@@ -49,6 +51,7 @@
         "playwright": "^1.56.1",
         "sharp": "^0.34.5",
         "uuid": "^13.0.0",
+        "web-push": "^3.6.7",
         "zod": "^3.23.0"
     }
 }