test(playwright): add playwright report to track changes + correct playwright parameters

ci: fix actions/checkout@v6 → @v4 (v6 does not exist)

GitHub started rejecting invalid action versions at parse time,
causing every CI run to fail with 0s / 'workflow file issue'
before any jobs could start.

 * test(e2e): only no retry
 * test(e2e): use static name in tests to facilitate screenshot comparaison
 * test(e2e): update linux screenshots
 * test(e2e): adapt test due to user-vignette generation

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

tests/e2e/package.json

@@ -5,7 +5,7 @@
   "main": "index.js",
   "scripts": {
     "pretest": "bash ../common/spawn-db.sh",
-    "test": "npx playwright test --reporter=line,github --trace=on-first-retry scenarios/01-home-and-login.spec.ts scenarios/02-folder-management.spec.ts",
+    "test": "FORCE_COLOR=true npx playwright test scenarios/01-home-and-login.spec.ts scenarios/02-folder-management.spec.ts",
     "posttest": "bash ../common/stop-db.sh"
   },
   "keywords": [],