refactor(ui): rename route /korrespondenz → /briefwechsel

Update all internal links (AppNav, CoCorrespondentsList, goto) to the
new URL. No redirect needed — no production URLs exist yet.

Refs: #179

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

frontend/src/routes/briefwechsel/CorrespondenzPersonBar.svelte

@@ -0,0 +1,129 @@
+<script lang="ts">
+import PersonTypeahead from '$lib/components/PersonTypeahead.svelte';
+import CorrespondentSuggestionsDropdown from './CorrespondentSuggestionsDropdown.svelte';
+
+interface Props {
+	senderId?: string;
+	receiverId?: string;
+	initialSenderName?: string;
+	initialReceiverName?: string;
+	onapplyFilters: () => void;
+	onswapPersons: () => void;
+}
+
+let {
+	senderId = $bindable(''),
+	receiverId = $bindable(''),
+	initialSenderName = '',
+	initialReceiverName = '',
+	onapplyFilters,
+	onswapPersons
+}: Props = $props();
+
+interface Correspondent {
+	id: string;
+	firstName: string;
+	lastName: string;
+}
+
+let swapVisible = $derived(!!(senderId && receiverId));
+
+let showSuggestions = $state(false);
+let correspondents = $state<Correspondent[]>([]);
+let loadingCorrespondents = $state(false);
+
+async function handleCorrespondentFocused() {
+	if (!senderId) return;
+	showSuggestions = true;
+	loadingCorrespondents = true;
+	try {
+		const res = await fetch(`/api/persons/${senderId}/correspondents`);
+		correspondents = res.ok ? await res.json() : [];
+	} catch {
+		correspondents = [];
+	} finally {
+		loadingCorrespondents = false;
+	}
+}
+
+function handleSuggestionSelect(id: string) {
+	receiverId = id;
+	showSuggestions = false;
+	onapplyFilters();
+}
+</script>
+
+<div class="flex items-end gap-[9px] border-b border-line bg-surface px-4 py-[9px] sm:px-[18px]">
+	<!-- Person A -->
+	<div class="min-w-0 flex-1">
+		<PersonTypeahead
+			name="senderId"
+			label="Person"
+			bind:value={senderId}
+			initialName={initialSenderName}
+			compact={true}
+			restrictToCorrespondentsOf={receiverId || undefined}
+			onchange={() => onapplyFilters()}
+		/>
+	</div>
+
+	<!-- Swap button -->
+	<button
+		data-testid="conv-swap-btn"
+		type="button"
+		aria-label="Personen tauschen"
+		onclick={onswapPersons}
+		class="flex h-9 w-9 shrink-0 items-center justify-center rounded border border-line bg-surface text-ink-3 transition-colors hover:border-primary hover:text-primary"
+		class:opacity-0={!swapVisible}
+		class:pointer-events-none={!swapVisible}
+		tabindex={swapVisible ? 0 : -1}
+	>
+		<svg
+			xmlns="http://www.w3.org/2000/svg"
+			width="14"
+			height="14"
+			viewBox="0 0 24 24"
+			fill="none"
+			stroke="currentColor"
+			stroke-width="2"
+			stroke-linecap="round"
+			stroke-linejoin="round"
+			aria-hidden="true"
+		>
+			<path d="M7 16V4m0 0L3 8m4-4l4 4" />
+			<path d="M17 8v12m0 0l4-4m-4 4l-4-4" />
+		</svg>
+	</button>
+
+	<!-- Korrespondent field -->
+	<div
+		class="relative min-w-0 flex-1"
+		class:[&_input]:border-dashed={!receiverId}
+		class:[&_input]:border-solid={!!receiverId}
+		class:[&_input]:bg-canvas={!receiverId}
+	>
+		<PersonTypeahead
+			name="receiverId"
+			label={receiverId ? 'Korrespondent' : 'Korrespondent — optional'}
+			bind:value={receiverId}
+			initialName={initialReceiverName}
+			compact={true}
+			placeholder="Alle Korrespondenten"
+			restrictToCorrespondentsOf={senderId || undefined}
+			onchange={() => {
+				showSuggestions = false;
+				onapplyFilters();
+			}}
+			onfocused={handleCorrespondentFocused}
+		/>
+		{#if showSuggestions && senderId && !receiverId}
+			<CorrespondentSuggestionsDropdown
+				correspondents={correspondents}
+				loading={loadingCorrespondents}
+				senderName=""
+				onselect={handleSuggestionSelect}
+				onclose={() => (showSuggestions = false)}
+			/>
+		{/if}
+	</div>
+</div>