i18n(briefwechsel): ThumbnailRow direction label via Paraglide

Adds row_direction_sent / row_direction_received keys across the
three locale files (de: Gesendet/Empfangen, en: Sent/Received, es:
Enviada/Recibida) and routes ThumbnailRow's directionLabel through
Paraglide. An English or Spanish screen-reader user now hears
"Sent:" / "Enviada:" in their language, matching the DistributionBar
i18n pass.

Refs #305
Fixes @leonievoss round-2 follow-up from PR review

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

frontend/messages/de.json

@@ -167,6 +167,8 @@
 	"conv_no_party": "—",
 	"dist_bar_segment": "{count} von {name}",
 	"dist_bar_aria": "Briefverteilung in diesem Zeitraum: {outCount} von {senderName}, {inCount} von {receiverName}",
+	"row_direction_sent": "Gesendet",
+	"row_direction_received": "Empfangen",
 	"admin_heading": "Admin Dashboard",
 	"admin_tab_users": "Benutzer",
 	"admin_tab_groups": "Gruppen",

frontend/messages/en.json

@@ -167,6 +167,8 @@
 	"conv_no_party": "—",
 	"dist_bar_segment": "{count} from {name}",
 	"dist_bar_aria": "Letter distribution in this period: {outCount} from {senderName}, {inCount} from {receiverName}",
+	"row_direction_sent": "Sent",
+	"row_direction_received": "Received",
 	"admin_heading": "Admin Dashboard",
 	"admin_tab_users": "Users",
 	"admin_tab_groups": "Groups",

frontend/messages/es.json

@@ -167,6 +167,8 @@
 	"conv_no_party": "—",
 	"dist_bar_segment": "{count} de {name}",
 	"dist_bar_aria": "Distribución de cartas en este período: {outCount} de {senderName}, {inCount} de {receiverName}",
+	"row_direction_sent": "Enviada",
+	"row_direction_received": "Recibida",
 	"admin_heading": "Panel de administración",
 	"admin_tab_users": "Usuarios",
 	"admin_tab_groups": "Grupos",

frontend/src/lib/components/ThumbnailRow.svelte

@@ -3,6 +3,7 @@ import ConversationThumbnail from '$lib/components/ConversationThumbnail.svelte'
 import TagChipList from '$lib/components/TagChipList.svelte';
 import { formatDate } from '$lib/utils/date';
 import { relativeYearsDe } from '$lib/relativeTime';
+import * as m from '$lib/paraglide/messages.js';
 
 type Person = { id: string; firstName?: string | null; lastName: string; displayName: string };
 type Tag = { id: string; name: string };
@@ -47,7 +48,7 @@ const otherPartyName = $derived(
 const relativeYearLabel = $derived(
 	doc.documentDate ? relativeYearsDe(new Date(doc.documentDate + 'T12:00:00'), now) : ''
 );
-const directionLabel = $derived(isOut ? 'Gesendet' : 'Empfangen');
+const directionLabel = $derived(isOut ? m.row_direction_sent() : m.row_direction_received());
 const ariaLabel = $derived(
 	`${directionLabel}: ${title}${doc.documentDate ? `, ${formatDate(doc.documentDate)}` : ''}`
 );

frontend/src/lib/components/ThumbnailRow.svelte.spec.ts

@@ -1,5 +1,6 @@
 import { describe, it, expect, afterEach } from 'vitest';
 import { cleanup, render } from 'vitest-browser-svelte';
+import * as m from '$lib/paraglide/messages.js';
 
 import ThumbnailRow from './ThumbnailRow.svelte';
 
@@ -151,12 +152,14 @@ describe('ThumbnailRow', () => {
 
 		const link = document.querySelector('a[href="/documents/d1"]') as HTMLElement;
 		const label = link.getAttribute('aria-label') ?? '';
-		expect(label).toMatch(/^Gesendet:/);
+		// Direction label routes through Paraglide so EN / ES users don't hear
+		// "Gesendet" in their screen reader.
+		expect(label.startsWith(`${m.row_direction_sent()}:`)).toBe(true);
 		expect(label).toContain('Liebe Anna');
 		expect(label).toMatch(/1950/);
 	});
 
-	it('aria-label begins with "Empfangen:" for incoming letters', () => {
+	it('aria-label leads with the received direction label for incoming letters', () => {
 		render(ThumbnailRow, {
 			doc: baseDoc,
 			isOut: false,
@@ -165,7 +168,8 @@ describe('ThumbnailRow', () => {
 		});
 
 		const link = document.querySelector('a[href="/documents/d1"]') as HTMLElement;
-		expect(link.getAttribute('aria-label') ?? '').toMatch(/^Empfangen:/);
+		const label = link.getAttribute('aria-label') ?? '';
+		expect(label.startsWith(`${m.row_direction_received()}:`)).toBe(true);
 	});
 
 	it('does not inject raw HTML when summary contains markup (XSS regression)', () => {