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/

playwright.config.js

@@ -0,0 +1,12 @@
+// @ts-check
+const { defineConfig } = require('@playwright/test');
+
+module.exports = defineConfig({
+  testDir: './test/e2e',
+  timeout: 30000,
+  retries: 0,
+  use: {
+    baseURL: process.env.SIS_URL || 'http://localhost:8080',
+    headless: true,
+  },
+});