fix(picker): honest combobox — keyboard navigation, listbox roles, no-results state

The input declared role=combobox + aria-autocomplete=list while arrow keys
did nothing (WCAG 4.1.2). Wired the useTypeahead activeIndex the same way
PersonTypeahead does: ArrowUp/Down cycle, Enter/Space select, Escape closes,
aria-activedescendant tracks the active option; the list is a real listbox
with option roles again (the interim role downgrade is reverted). Zero hits
now render a 'Keine Treffer' row instead of silently vanishing, aria-expanded
matches the visible state, and the hook sets loading at setQuery so the
debounce window can't read as 'no results'. DocumentMultiSelect renders the
shared error state too. _uid counter replaced with $props.id().

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/messages/de.json

@@ -302,6 +302,7 @@
 	"comp_multiselect_remove": "Entfernen",
 	"comp_multiselect_loading": "Suche...",
 	"comp_typeahead_error": "Suche fehlgeschlagen. Bitte versuchen Sie es erneut.",
+	"comp_typeahead_no_results": "Keine Treffer",
 	"comp_taginput_placeholder_create": "Schlagworte hinzufügen...",
 	"comp_taginput_placeholder_filter": "Nach Schlagworten filtern...",
 	"comp_taginput_remove": "Schlagwort entfernen",
@@ -1179,6 +1180,11 @@
 	"journey_selector_aria_live_hint": "Bitte wähle einen Typ aus, um fortzufahren.",
 	"journey_add_document": "Brief hinzufügen",
 	"journey_add_interlude": "Zwischentext hinzufügen",
+	"journey_interlude_label": "Zwischentext",
+	"journey_item_pending_remove": "wird entfernt…",
+	"journey_publish_disabled_hint": "Titel und mindestens ein Eintrag erforderlich.",
+	"journey_title_aria_label": "Titel der Lesereise",
+	"journey_intro_aria_label": "Einleitung der Lesereise",
 	"journey_note_add": "Notiz hinzufügen",
 	"journey_note_remove": "Notiz entfernen",
 	"journey_note_save_hint": "Wird gespeichert, wenn du das Feld verlässt.",