feat(frontend): new strip components, suggestions dropdown, empty state

CorrespondenzPersonBar (Row 1), CorrespondenzFilterControls (Row 2 with
live count + sort), CorrespondentSuggestionsDropdown (fetch-on-focus,
keyboard nav), SinglePersonHintBar, CorrespondenzEmptyState (recent
persons from localStorage). New i18n shim in messages-extra.ts until
root-owned paraglide files can be regenerated.

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

frontend/src/routes/korrespondenz/CorrespondenzPersonBar.svelte

@@ -0,0 +1,87 @@
+<script lang="ts">
+import PersonTypeahead from '$lib/components/PersonTypeahead.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();
+
+let swapVisible = $derived(!!(senderId && receiverId));
+</script>
+
+<div class="flex items-end gap-[9px] border-b border-[#EAE7E0] bg-white 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}
+			restrictToCorrespondentsOf={receiverId || undefined}
+			onchange={() => onapplyFilters()}
+		/>
+	</div>
+
+	<!-- Swap button -->
+	<button
+		data-testid="conv-swap-btn"
+		type="button"
+		aria-label="Personen tauschen"
+		onclick={onswapPersons}
+		class="mb-1 flex h-7 w-7 shrink-0 items-center justify-center rounded border border-[#D1D5DB] bg-white text-[#888] transition-colors hover:border-[#002850] hover:text-[#002850]"
+		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="min-w-0 flex-1"
+		class:[&_input]:border-dashed={!receiverId}
+		class:[&_input]:border-solid={!!receiverId}
+		class:[&_input]:bg-[#F9F8F6]={!receiverId}
+	>
+		<PersonTypeahead
+			name="receiverId"
+			label={receiverId ? 'Korrespondent' : 'Korrespondent'}
+			bind:value={receiverId}
+			initialName={initialReceiverName}
+			restrictToCorrespondentsOf={senderId || undefined}
+			onchange={() => onapplyFilters()}
+		/>
+		{#if !receiverId}
+			<span class="pointer-events-none absolute -mt-[1px] text-[11px] text-[#AAA] italic">
+				— optional
+			</span>
+		{/if}
+	</div>
+</div>