feat(frontend): rename route to /korrespondenz, update i18n, regen API types

Moves conversations/ to korrespondenz/, updates all internal links,
renames nav label and page heading to Korrespondenz across de/en/es,
and adds all new i18n keys for the redesigned strip and log.

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

frontend/src/routes/korrespondenz/+page.server.ts

@@ -0,0 +1,64 @@
+import type { components } from '$lib/generated/api';
+import { createApiClient } from '$lib/api.server';
+
+export async function load({ url, fetch }) {
+	const senderId = url.searchParams.get('senderId') || '';
+	const receiverId = url.searchParams.get('receiverId') || '';
+	const from = url.searchParams.get('from') || '';
+	const to = url.searchParams.get('to') || '';
+	const dir = url.searchParams.get('dir') || 'DESC';
+
+	const api = createApiClient(fetch);
+
+	let documents: components['schemas']['Document'][] = [];
+	let senderName = '';
+	let receiverName = '';
+
+	const requests: Promise<void>[] = [];
+
+	if (senderId && receiverId) {
+		requests.push(
+			api
+				.GET('/api/documents/conversation', {
+					params: {
+						query: {
+							senderId,
+							receiverId,
+							dir,
+							from: from || undefined,
+							to: to || undefined
+						}
+					}
+				})
+				.then(({ data }) => {
+					documents = data ?? [];
+				})
+		);
+	}
+
+	if (senderId) {
+		requests.push(
+			api.GET('/api/persons/{id}', { params: { path: { id: senderId } } }).then(({ data }) => {
+				const p = data as { firstName: string; lastName: string } | undefined;
+				if (p) senderName = `${p.firstName} ${p.lastName}`;
+			})
+		);
+	}
+
+	if (receiverId) {
+		requests.push(
+			api.GET('/api/persons/{id}', { params: { path: { id: receiverId } } }).then(({ data }) => {
+				const p = data as { firstName: string; lastName: string } | undefined;
+				if (p) receiverName = `${p.firstName} ${p.lastName}`;
+			})
+		);
+	}
+
+	await Promise.all(requests);
+
+	return {
+		documents,
+		initialValues: { senderName, receiverName },
+		filters: { senderId, receiverId, from, to, dir }
+	};
+}