feat(korrespondenz): address PR #164 review – blockers and suggestions

Blockers (14):
- B1: fix senderName/receiverName to use $derived instead of $state + sync $effect
- B2: migrate all korrespondenz components from messages-extra shim to paraglide m.*
- B3: i18n CorrespondenzEmptyState (heading, subtext, search placeholder)
- B4: add response.ok checks to admin layout server load
- B5: add response.ok checks to korrespondenz page server load
- B6: add page.server.spec.ts with 5 test suites for korrespondenz load function
- B7: add axe-core accessibility checks to all e2e korrespondenz tests
- B8: add Testcontainers JPQL tests for findSinglePersonCorrespondence (DISTINCT + sender)
- B9: hide auth reset-token endpoint from OpenAPI spec; remove from generated api.ts
- B11: replace amber hardcoded hex colors in SinglePersonHintBar with brand tokens
- B12: replace clipboard emoji with Heroicons SVG in SinglePersonHintBar
- B13: create DateInput component (German dd.mm.yyyy); use it in CorrespondenzFilterControls
- B14: add Paraglide compile step to CI workflow before lint/test

Suggestions (11):
- S1: make CorrespondentSuggestionsDropdown a pure display component; lift fetch to PersonBar
- S2: fix leftover messages-extra import in ConversationTimeline; use brand tokens for status dots
- S3: add intent comment to EntityNav openFlyout behavior
- S4: rename canManageGroups → canManagePermissions throughout admin
- S6: remove domFlush helper from DateInput spec; use expect.poll instead
- S7: replace test.skip with throw new Error in bilateral e2e tests
- S8: add inverse aria-disabled test for filter strip
- S9: remove sm:min-h-0 from sort button to preserve 44px touch target
- S10: add title attributes to tablet trigger buttons in EntityNav
- S11: delete messages-extra.ts shim entirely

Also: fix admin pages revealing blank strip at bottom (-mb-6 on admin layout)

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

frontend/src/routes/admin/EntityNav.svelte

@@ -10,7 +10,7 @@ let {
 	tagCount,
 	canManageUsers,
 	canManageTags,
-	canManageGroups,
+	canManagePermissions,
 	canRunMaintenance
 }: {
 	userCount: number;
@@ -18,7 +18,7 @@ let {
 	tagCount: number;
 	canManageUsers: boolean;
 	canManageTags: boolean;
-	canManageGroups: boolean;
+	canManagePermissions: boolean;
 	canRunMaintenance: boolean;
 } = $props();
 
@@ -28,6 +28,9 @@ const isActive = (section: string) => currentPath.startsWith(`/admin/${section}`
 let flyoutOpen = $state(false);
 let flyoutTriggerElement: HTMLButtonElement | null = null;
 
+// All four section buttons open the same flyout that repeats the full nav.
+// This is intentional: on tablet the flyout shows all sections as a wider navigation panel,
+// not a context-specific panel for the clicked section.
 async function openFlyout(event: MouseEvent) {
 	flyoutTriggerElement = event.currentTarget as HTMLButtonElement;
 	flyoutOpen = true;
@@ -71,6 +74,7 @@ function handleKeydown(event: KeyboardEvent) {
 			data-flyout-trigger
 			type="button"
 			aria-label={m.admin_tab_users()}
+			title={m.admin_tab_users()}
 			onclick={openFlyout}
 			class="flex min-h-[44px] w-full flex-col items-center justify-center gap-0.5 border-l-[3px] py-3 transition-colors lg:hidden
 				{isActive('users')
@@ -131,12 +135,13 @@ function handleKeydown(event: KeyboardEvent) {
 		</a>
 	{/if}
 
-	{#if canManageGroups}
+	{#if canManagePermissions}
 		<!-- Tablet trigger button (md only, hidden at lg) -->
 		<button
 			data-flyout-trigger
 			type="button"
 			aria-label={m.admin_tab_groups()}
+			title={m.admin_tab_groups()}
 			onclick={openFlyout}
 			class="flex min-h-[44px] w-full flex-col items-center justify-center gap-0.5 border-l-[3px] py-3 transition-colors lg:hidden
 				{isActive('groups')
@@ -203,6 +208,7 @@ function handleKeydown(event: KeyboardEvent) {
 			data-flyout-trigger
 			type="button"
 			aria-label={m.admin_tab_tags()}
+			title={m.admin_tab_tags()}
 			onclick={openFlyout}
 			class="flex min-h-[44px] w-full flex-col items-center justify-center gap-0.5 border-l-[3px] py-3 transition-colors lg:hidden
 				{isActive('tags')
@@ -273,6 +279,7 @@ function handleKeydown(event: KeyboardEvent) {
 			data-flyout-trigger
 			type="button"
 			aria-label={m.admin_tab_system()}
+			title={m.admin_tab_system()}
 			onclick={openFlyout}
 			class="flex min-h-[44px] w-full flex-col items-center justify-center gap-0.5 border-t border-l-[3px] border-white/10 py-3 transition-colors lg:hidden
 				{isActive('system')
@@ -390,7 +397,7 @@ function handleKeydown(event: KeyboardEvent) {
 			</a>
 		{/if}
 
-		{#if canManageGroups}
+		{#if canManagePermissions}
 			<a
 				href="/admin/groups"
 				onclick={closeFlyout}