chore(test): Playwright für PWA-E2E-Tests aufgesetzt

@playwright/test + chromium als devDep. playwright.config.ts
startet npm run preview (production build nötig für SW), baseURL
localhost:4173, fullyParallel off (SW-Installations-Timing). Ein
Smoke-Test smoke.spec.ts öffnet / und prüft den Titel. test-results/
und playwright-report/ in .gitignore ergänzt.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package-lock.json

@@ -18,6 +18,7 @@
         "zod": "^3.23.8"
       },
       "devDependencies": {
+        "@playwright/test": "^1.59.1",
         "@sveltejs/adapter-node": "^5.2.0",
         "@sveltejs/kit": "^2.8.0",
         "@sveltejs/vite-plugin-svelte": "^4.0.0",
@@ -1220,6 +1221,22 @@
         "node": ">=14"
       }
     },
+    "node_modules/@playwright/test": {
+      "version": "1.59.1",
+      "resolved": "https://registry.npmjs.org/@playwright/test/-/test-1.59.1.tgz",
+      "integrity": "sha512-PG6q63nQg5c9rIi4/Z5lR5IVF7yU5MqmKaPOe0HSc0O2cX1fPi96sUQu5j7eo4gKCkB2AnNGoWt7y4/Xx3Kcqg==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "dependencies": {
+        "playwright": "1.59.1"
+      },
+      "bin": {
+        "playwright": "cli.js"
+      },
+      "engines": {
+        "node": ">=18"
+      }
+    },
     "node_modules/@polka/url": {
       "version": "1.0.0-next.29",
       "resolved": "https://registry.npmjs.org/@polka/url/-/url-1.0.0-next.29.tgz",
@@ -3744,6 +3761,53 @@
         "url": "https://github.com/sponsors/jonschlinkert"
       }
     },
+    "node_modules/playwright": {
+      "version": "1.59.1",
+      "resolved": "https://registry.npmjs.org/playwright/-/playwright-1.59.1.tgz",
+      "integrity": "sha512-C8oWjPR3F81yljW9o5OxcWzfh6avkVwDD2VYdwIGqTkl+OGFISgypqzfu7dOe4QNLL2aqcWBmI3PMtLIK233lw==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "dependencies": {
+        "playwright-core": "1.59.1"
+      },
+      "bin": {
+        "playwright": "cli.js"
+      },
+      "engines": {
+        "node": ">=18"
+      },
+      "optionalDependencies": {
+        "fsevents": "2.3.2"
+      }
+    },
+    "node_modules/playwright-core": {
+      "version": "1.59.1",
+      "resolved": "https://registry.npmjs.org/playwright-core/-/playwright-core-1.59.1.tgz",
+      "integrity": "sha512-HBV/RJg81z5BiiZ9yPzIiClYV/QMsDCKUyogwH9p3MCP6IYjUFu/MActgYAvK0oWyV9NlwM3GLBjADyWgydVyg==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "bin": {
+        "playwright-core": "cli.js"
+      },
+      "engines": {
+        "node": ">=18"
+      }
+    },
+    "node_modules/playwright/node_modules/fsevents": {
+      "version": "2.3.2",
+      "resolved": "https://registry.npmjs.org/fsevents/-/fsevents-2.3.2.tgz",
+      "integrity": "sha512-xiqMQR4xAeHTuB9uWm+fFRcIOgKBMiOBP+eXiyT7jsgVCq1bkVygt00oASowB7EdtpOHaaPgKt812P9ab+DDKA==",
+      "dev": true,
+      "hasInstallScript": true,
+      "license": "MIT",
+      "optional": true,
+      "os": [
+        "darwin"
+      ],
+      "engines": {
+        "node": "^8.16.0 || ^10.6.0 || >=11.0.0"
+      }
+    },
     "node_modules/postcss": {
       "version": "8.5.10",
       "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.5.10.tgz",