fix(documents): sync filter display state with URL on navigation

Three root causes prevented filters from reflecting the URL after SvelteKit
client-side navigation:

1. +page.server.ts now resolves sender/receiver display names in parallel with
   the document search (UUID validation + silent 404 drop), so initialSenderName
   / initialReceiverName land in server data ready for the UI to use.

2. +page.svelte passes initialSenderName, initialReceiverName, and navKey
   (incremented via untrack on every navigation) down to SearchFilterBar.
   The untrack() prevents the effect from re-running due to its own navKey write.

3. SearchFilterBar forwards navKey as resetKey to each PersonTypeahead, which
   already had a void resetKey guard added in the previous commit.

Together these ensure that after navigating to /documents?senderId=<uuid> the
typeahead shows the person's display name, and clicking × reset clears it.

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

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

@@ -3,6 +3,20 @@ import { createApiClient } from '$lib/shared/api.server';
 import { getErrorMessage } from '$lib/shared/errors';
 import type { components } from '$lib/generated/api';
 
+const UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;
+
+async function resolvePersonName(id: string, fetch: typeof globalThis.fetch): Promise<string> {
+	if (!UUID_RE.test(id)) return '';
+	try {
+		const res = await fetch(`/api/persons/${id}`);
+		if (!res.ok) return '';
+		const person = await res.json();
+		return person.displayName ?? '';
+	} catch {
+		return '';
+	}
+}
+
 type DocumentSearchItem = components['schemas']['DocumentSearchItem'];
 
 const VALID_SORTS = ['DATE', 'TITLE', 'SENDER', 'RECEIVER', 'UPLOAD_DATE', 'RELEVANCE'] as const;
@@ -34,25 +48,30 @@ export async function load({ url, fetch }) {
 	const api = createApiClient(fetch);
 
 	let result;
+	let initialSenderName = '';
+	let initialReceiverName = '';
 	try {
-		result = await api.GET('/api/documents/search', {
-			params: {
-				query: {
-					q: q || undefined,
-					from: from || undefined,
-					to: to || undefined,
-					senderId: senderId || undefined,
-					receiverId: receiverId || undefined,
-					tag: tags.length ? tags : undefined,
-					tagQ: tagQ && !tags.length ? tagQ : undefined,
-					tagOp: tagOp === 'OR' ? 'OR' : undefined,
-					sort,
-					dir: dir || undefined,
-					page,
-					size: PAGE_SIZE
+		[result, [initialSenderName, initialReceiverName]] = await Promise.all([
+			api.GET('/api/documents/search', {
+				params: {
+					query: {
+						q: q || undefined,
+						from: from || undefined,
+						to: to || undefined,
+						senderId: senderId || undefined,
+						receiverId: receiverId || undefined,
+						tag: tags.length ? tags : undefined,
+						tagQ: tagQ && !tags.length ? tagQ : undefined,
+						tagOp: tagOp === 'OR' ? 'OR' : undefined,
+						sort,
+						dir: dir || undefined,
+						page,
+						size: PAGE_SIZE
+					}
 				}
-			}
-		});
+			}),
+			Promise.all([resolvePersonName(senderId, fetch), resolvePersonName(receiverId, fetch)])
+		]);
 	} catch {
 		return {
 			items: [] as DocumentSearchItem[],
@@ -65,6 +84,8 @@ export async function load({ url, fetch }) {
 			to,
 			senderId,
 			receiverId,
+			initialSenderName: '',
+			initialReceiverName: '',
 			tags,
 			sort,
 			dir,
@@ -94,6 +115,8 @@ export async function load({ url, fetch }) {
 		to,
 		senderId,
 		receiverId,
+		initialSenderName,
+		initialReceiverName,
 		tags,
 		sort,
 		dir,