feat: add Playwright e2e smoke test covering signup → household → chore flow

- Added smoke.spec.js with Playwright test for full user flow:
  1. Sign up (fill form, submit, click 'Go to Dashboard')
  2. Create household (fill name, submit)
  3. Create chore (fill name + date, submit)
  4. Verify session persistence (revisit dashboard)
- Server now supports --db flag for temp databases and SIS_FRESH_DB env
  to delete the db file on startup (for clean test runs)
- Server reads SIS_PORT env var for port configuration
- scripts/test-e2e: starts server with fresh db, runs tests, cleans up
- playwright.config.js: minimal config pointing at test/e2e/

package.json

@@ -1,5 +1,6 @@
 {
   "dependencies": {
+    "@playwright/test": "^1.61.1",
     "playwright": "^1.61.1"
   }
 }