fix(korrespondenz): address 10 visual and functional regressions

- Strip full-bleed: remove max-w container, put strips at page level
- Remove page heading/subtitle above strip (not in spec)
- Swap button always visible (drop opacity-0, keep pointer-events-none)
- Korrespondent placeholder "Alle Korrespondenten" + label "— optional"
- Add placeholder prop to PersonTypeahead; add onfocused callback prop
- "Person suchen" button now focuses #senderId-search instead of no-op navigate
- Wire CorrespondentSuggestionsDropdown on correspondent field focus
- Hint bar: bold name via <strong>, year-only dates (no ISO strings)
- Asymmetry bar: use first name only to prevent label overflow

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

frontend/src/routes/korrespondenz/SinglePersonHintBar.svelte

@@ -1,10 +1,5 @@
 <script lang="ts">
-import {
-	conv_hint_single_person,
-	conv_hint_single_person_filtered,
-	conv_strip_sort_newest,
-	conv_strip_sort_oldest
-} from '$lib/messages-extra';
+import { conv_strip_sort_newest, conv_strip_sort_oldest } from '$lib/messages-extra';
 
 interface Props {
 	senderName: string;
@@ -16,8 +11,9 @@ interface Props {
 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());
+let fromYear = $derived(fromDate ? fromDate.substring(0, 4) : '');
+let toYear = $derived(toDate ? toDate.substring(0, 4) : '');
 </script>
 
 <div
@@ -26,13 +22,12 @@ let sortLabel = $derived(sortDir === 'ASC' ? conv_strip_sort_oldest() : conv_str
 	<span class="text-sm" aria-hidden="true">📋</span>
 
 	{#if hasDateFilter}
-		{conv_hint_single_person_filtered({
-			name: senderName,
-			from: fromDate ?? '',
-			to: toDate ?? '',
-			sortLabel
-		})}
+		<strong>{senderName}</strong>
+		<span>·</span>
+		<span>{fromYear}–{toYear}</span>
+		<span>·</span>
+		<span>{sortLabel}</span>
 	{:else}
-		{conv_hint_single_person({ name: senderName })}
+		Alle Briefe von <strong>{senderName}</strong> — wähle einen Korrespondenten oben um einzugrenzen
 	{/if}
 </div>