Add Playwright test suite (51 tests, all passing)

- tests/api.spec.js: 17 tests covering public booking API and admin CRUD
  (health, POST bookings, auth rejection, stats, filters, PATCH, CSV export)
- tests/booking.spec.js: 12 tests covering the 7-step booking wizard
  (open/close, date validation, step progression, contract scroll+signature,
  payment checkbox, full end-to-end booking flow)
- tests/dashboard.spec.js: 15 tests covering the admin dashboard
  (login, wrong passphrase, Enter key, sign out, overview stats, calendar
  month nav, bookings table, search filter, row expand, CSV download)
- tests/portfolio.spec.js: 7 tests covering the portfolio site
  (nav, book button, portfolio section, config, health, theme color)
- playwright.config.js: Chromium headless, BASE_URL + ADMIN_SECRET via env
- Fix dangling client-email input outside step-panel (was visible, making
  the booking modal taller and hiding the Next button in headless mode)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -0,0 +1,25 @@
+{
+  "name": "lisilou-portfolio",
+  "version": "1.0.0",
+  "description": "A lightweight, configurable photography portfolio website designed to integrate with Immich for image hosting and client gallery access.",
+  "main": "index.js",
+  "scripts": {
+    "test": "playwright test",
+    "test:headed": "playwright test --headed",
+    "test:ui": "playwright test --ui"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/jhodgkin/lisilou-portfolio.git"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "bugs": {
+    "url": "https://github.com/jhodgkin/lisilou-portfolio/issues"
+  },
+  "homepage": "https://github.com/jhodgkin/lisilou-portfolio#readme",
+  "devDependencies": {
+    "@playwright/test": "^1.61.1"
+  }
+}