feat(i18n): add sort, result count, and empty-state translation keys

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

frontend/messages/de.json

@@ -52,7 +52,15 @@
 	"login_label_username": "Benutzername",
 	"login_label_password": "Passwort",
 	"login_btn_submit": "Anmelden",
-	"docs_search_placeholder": "Suche in Titel, Inhalt, Ort...",
+	"docs_search_placeholder": "Titel, Personen, Tags durchsuchen…",
+	"docs_sort_label": "Sortierung",
+	"docs_sort_date": "Datum",
+	"docs_sort_title": "Titel",
+	"docs_sort_sender": "Absender",
+	"docs_sort_receiver": "Empfänger",
+	"docs_sort_upload": "Hochgeladen",
+	"docs_result_count": "{count} Dokumente",
+	"docs_empty_for_term": "Keine Dokumente f\u00fcr \"{term}\" gefunden",
 	"docs_btn_filter": "Filter",
 	"docs_btn_reset_title": "Filter zurücksetzen",
 	"docs_filter_label_tags": "Schlagworte",

frontend/messages/en.json

@@ -52,7 +52,15 @@
 	"login_label_username": "Username",
 	"login_label_password": "Password",
 	"login_btn_submit": "Sign in",
-	"docs_search_placeholder": "Search in title, content, location...",
+	"docs_search_placeholder": "Search title, people, tags…",
+	"docs_sort_label": "Sort",
+	"docs_sort_date": "Date",
+	"docs_sort_title": "Title",
+	"docs_sort_sender": "Sender",
+	"docs_sort_receiver": "Receiver",
+	"docs_sort_upload": "Uploaded",
+	"docs_result_count": "{count} documents",
+	"docs_empty_for_term": "No documents found for \"{term}\"",
 	"docs_btn_filter": "Filter",
 	"docs_btn_reset_title": "Reset filter",
 	"docs_filter_label_tags": "Tags",

frontend/messages/es.json

@@ -52,7 +52,15 @@
 	"login_label_username": "Usuario",
 	"login_label_password": "Contraseña",
 	"login_btn_submit": "Iniciar sesión",
-	"docs_search_placeholder": "Buscar en título, contenido, lugar...",
+	"docs_search_placeholder": "Buscar título, personas, etiquetas…",
+	"docs_sort_label": "Ordenar",
+	"docs_sort_date": "Fecha",
+	"docs_sort_title": "Título",
+	"docs_sort_sender": "Remitente",
+	"docs_sort_receiver": "Destinatario",
+	"docs_sort_upload": "Subido",
+	"docs_result_count": "{count} documentos",
+	"docs_empty_for_term": "No se encontraron documentos para \"{term}\"",
 	"docs_btn_filter": "Filtrar",
 	"docs_btn_reset_title": "Restablecer filtro",
 	"docs_filter_label_tags": "Etiquetas",