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/SinglePersonHintBar.svelte

@@ -0,0 +1,38 @@
+<script lang="ts">
+import {
+	conv_hint_single_person,
+	conv_hint_single_person_filtered,
+	conv_strip_sort_newest,
+	conv_strip_sort_oldest
+} from '$lib/messages-extra';
+
+interface Props {
+	senderName: string;
+	fromDate?: string;
+	toDate?: string;
+	sortDir?: string;
+}
+
+let { senderName, fromDate = '', toDate = '', sortDir = 'DESC' }: Props = $props();
+
+let hasDateFilter = $derived(!!(fromDate || toDate));
+
+let sortLabel = $derived(sortDir === 'ASC' ? conv_strip_sort_oldest() : conv_strip_sort_newest());
+</script>
+
+<div
+	class="flex items-center gap-[5px] border-b border-[#FDBA74] bg-[#FFF7ED] px-[18px] py-[6px] text-xs text-[#92400E]"
+>
+	<span class="text-sm" aria-hidden="true">📋</span>
+
+	{#if hasDateFilter}
+		{conv_hint_single_person_filtered({
+			name: senderName,
+			from: fromDate ?? '',
+			to: toDate ?? '',
+			sortLabel
+		})}
+	{:else}
+		{conv_hint_single_person({ name: senderName })}
+	{/if}
+</div>