test(#118): add axe-core wcag2a/wcag2aa accessibility checks to E2E suite

Installs @axe-core/playwright and adds e2e/accessibility.spec.ts covering:
- home, persons, admin (authenticated via stored admin session)
- login (unauthenticated context)

Uses wcag2a + wcag2aa tags. Violations are logged with impact level and
node count before the assertion fails, so the first run against the live
stack will produce a clear inventory of any issues to fix or exclude.

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

frontend/package-lock.json

@@ -13,6 +13,7 @@
 				"pdfjs-dist": "^5.5.207"
 			},
 			"devDependencies": {
+				"@axe-core/playwright": "^4.11.1",
 				"@eslint/compat": "^1.4.0",
 				"@eslint/js": "^9.39.1",
 				"@inlang/paraglide-js": "^2.5.0",
@@ -47,6 +48,19 @@
 				"vitest-browser-svelte": "^2.0.1"
 			}
 		},
+		"node_modules/@axe-core/playwright": {
+			"version": "4.11.1",
+			"resolved": "https://registry.npmjs.org/@axe-core/playwright/-/playwright-4.11.1.tgz",
+			"integrity": "sha512-mKEfoUIB1MkVTht0BGZFXtSAEKXMJoDkyV5YZ9jbBmZCcWDz71tegNsdTkIN8zc/yMi5Gm2kx7Z5YQ9PfWNAWw==",
+			"dev": true,
+			"license": "MPL-2.0",
+			"dependencies": {
+				"axe-core": "~4.11.1"
+			},
+			"peerDependencies": {
+				"playwright-core": ">= 1.0.0"
+			}
+		},
 		"node_modules/@babel/code-frame": {
 			"version": "7.29.0",
 			"resolved": "https://registry.npmjs.org/@babel/code-frame/-/code-frame-7.29.0.tgz",
@@ -2866,6 +2880,16 @@
 			"dev": true,
 			"license": "MIT"
 		},
+		"node_modules/axe-core": {
+			"version": "4.11.1",
+			"resolved": "https://registry.npmjs.org/axe-core/-/axe-core-4.11.1.tgz",
+			"integrity": "sha512-BASOg+YwO2C+346x3LZOeoovTIoTrRqEsqMa6fmfAV0P+U9mFr9NsyOEpiYvFjbc64NMrSswhV50WdXzdb/Z5A==",
+			"dev": true,
+			"license": "MPL-2.0",
+			"engines": {
+				"node": ">=4"
+			}
+		},
 		"node_modules/axobject-query": {
 			"version": "4.1.0",
 			"resolved": "https://registry.npmjs.org/axobject-query/-/axobject-query-4.1.0.tgz",