feat(person): add a curator "Ereignis für diese Person" link to PersonCard

A curator on a person's page can now seed a timeline event from that
person: a gated link to #781's /zeitstrahl/events/new?personId={id},
which prefills the person and returns to /persons/{id} on save. Hidden
for a Reader. New i18n key person_add_event in de/en/es.

Refs #842
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/messages/de.json

@@ -188,6 +188,7 @@
 	"person_hint_generation": "Generation in der Familie (G 0 = älteste Generation)",
 	"person_year_error": "Bitte eine vierstellige Jahreszahl eingeben",
 	"person_years_error_order": "Geburtsjahr muss vor dem Todesjahr liegen",
+	"person_add_event": "Ereignis für diese Person",
 	"person_docs_heading": "Gesendete Dokumente",
 	"person_no_docs": "Diese Person ist noch nicht als Absender verknüpft.",
 	"person_received_docs_heading": "Empfangene Dokumente",

frontend/messages/en.json

@@ -188,6 +188,7 @@
 	"person_hint_generation": "Generation within the family (G 0 = oldest generation)",
 	"person_year_error": "Please enter a four-digit year",
 	"person_years_error_order": "Birth year must be before death year",
+	"person_add_event": "Add event for this person",
 	"person_docs_heading": "Sent documents",
 	"person_no_docs": "This person has not yet been linked as a sender.",
 	"person_received_docs_heading": "Received documents",

frontend/messages/es.json

@@ -188,6 +188,7 @@
 	"person_hint_generation": "Generación dentro de la familia (G 0 = generación más antigua)",
 	"person_year_error": "Introduzca un año de cuatro dígitos",
 	"person_years_error_order": "El año de nacimiento debe ser anterior al año de fallecimiento",
+	"person_add_event": "Añadir evento para esta persona",
 	"person_docs_heading": "Documentos enviados",
 	"person_no_docs": "Esta persona aún no está vinculada como remitente.",
 	"person_received_docs_heading": "Documentos recibidos",