fix(#118): resolve wcag2a/wcag2aa violations found by axe-core suite

- Add <svelte:head><title> to home, persons, admin, login, and error pages
- Add aria-label to hidden file input in DropZone (sr-only but must be labelled)
- Add aria-label to search input in SearchFilterBar
- Create +error.svelte so error pages always have a document title
- axe-core spec: add buildAxe() helper, disable color-contrast (brand palette, tracked separately)

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

frontend/e2e/accessibility.spec.ts

@@ -6,9 +6,9 @@ import { test, expect } from '@playwright/test';
  * Authenticated pages use the stored admin session from playwright.config.ts.
  * The login page test overrides to an unauthenticated context.
  *
- * On first run: if violations are found they are logged with full details so
- * that they can be either fixed or explicitly excluded here with a comment
- * explaining the reason.
+ * Known exclusion:
+ *   color-contrast — brand palette (ink-3, text-ink/60) does not meet AA contrast
+ *   ratios. Requires a design review with Leonie before fixing. Tracked separately.
  */
 
 const AUTHENTICATED_PAGES = [
@@ -17,13 +17,17 @@ const AUTHENTICATED_PAGES = [
 	{ name: 'admin', path: '/admin' }
 ];
 
+function buildAxe(page: Parameters<typeof AxeBuilder>[0]['page']) {
+	return new AxeBuilder({ page }).withTags(['wcag2a', 'wcag2aa']).disableRules(['color-contrast']);
+}
+
 test.describe('Accessibility — authenticated pages', () => {
 	for (const { name, path } of AUTHENTICATED_PAGES) {
 		test(`${name} page has no critical wcag2a/wcag2aa violations`, async ({ page }) => {
 			await page.goto(path);
 			await page.waitForSelector('[data-hydrated]');
 
-			const results = await new AxeBuilder({ page }).withTags(['wcag2a', 'wcag2aa']).analyze();
+			const results = await buildAxe(page).analyze();
 
 			if (results.violations.length > 0) {
 				const summary = results.violations
@@ -44,7 +48,7 @@ test.describe('Accessibility — login page', () => {
 		await page.goto('/login');
 		await expect(page.getByLabel('Benutzername')).toBeVisible();
 
-		const results = await new AxeBuilder({ page }).withTags(['wcag2a', 'wcag2aa']).analyze();
+		const results = await buildAxe(page).analyze();
 
 		if (results.violations.length > 0) {
 			const summary = results.violations

frontend/src/routes/+error.svelte

@@ -0,0 +1,12 @@
+<script lang="ts">
+import { page } from '$app/state';
+</script>
+
+<svelte:head>
+	<title>Fehler – Familienarchiv</title>
+</svelte:head>
+
+<div class="px-4 py-12 text-center font-sans">
+	<p class="font-sans text-6xl font-bold text-ink">{page.status}</p>
+	<p class="mt-2 font-sans text-sm text-ink-2">{page.error?.message ?? 'Internal Error'}</p>
+</div>

frontend/src/routes/+page.svelte

@@ -67,6 +67,10 @@ $effect(() => {
 });
 </script>
 
+<svelte:head>
+	<title>Archiv</title>
+</svelte:head>
+
 <main class="mx-auto max-w-7xl px-4 py-8 font-sans sm:px-6 lg:px-8">
 	<SearchFilterBar
 		bind:q={q}

frontend/src/routes/DropZone.svelte

@@ -202,6 +202,7 @@ $effect(() => {
 	type="file"
 	multiple
 	accept=".pdf,.jpg,.jpeg,.png,.tif,.tiff"
+	aria-label={m.upload_label()}
 	class="sr-only"
 	onchange={handleFileSelect}
 />

frontend/src/routes/SearchFilterBar.svelte

@@ -44,6 +44,7 @@ let {
 				oninput={onSearch}
 				onfocus={onfocus}
 				onblur={onblur}
+				aria-label={m.docs_search_placeholder()}
 				placeholder={m.docs_search_placeholder()}
 				class="block w-full border-line py-2.5 pr-10 pl-3 placeholder-ink-3 shadow-sm focus:border-ink focus:ring-ink"
 			/>

frontend/src/routes/admin/+page.svelte

@@ -11,6 +11,10 @@ let { data, form } = $props();
 let activeTab = $state('users');
 </script>
 
+<svelte:head>
+	<title>Administration</title>
+</svelte:head>
+
 <div class="mx-auto max-w-7xl px-4 py-8 font-sans sm:px-6 lg:px-8">
 	<div class="mb-8 flex flex-col gap-4 sm:flex-row sm:items-center sm:justify-between">
 		<h1 class="font-serif text-3xl text-ink">{m.admin_heading()}</h1>

frontend/src/routes/login/+page.svelte

@@ -9,6 +9,10 @@ const localeMap = { DE: 'de', EN: 'en', ES: 'es' } as const;
 const activeLocale = $derived(getLocale().toUpperCase());
 </script>
 
+<svelte:head>
+	<title>Anmelden</title>
+</svelte:head>
+
 <div class="relative flex min-h-screen flex-col bg-canvas">
 	<!-- Language switcher -->
 	<div class="absolute top-4 right-4 flex items-center gap-1">

frontend/src/routes/persons/+page.svelte

@@ -23,6 +23,10 @@ function handleSearch() {
 }
 </script>
 
+<svelte:head>
+	<title>Personen</title>
+</svelte:head>
+
 <div class="mx-auto max-w-7xl px-4 py-12 sm:px-6 lg:px-8">
 	<!-- Header Area -->
 	<div