feat(relationship): date+precision edit UI, notes, and read-view display

Regenerate api.ts for the LocalDate+DatePrecision RelationshipDTO /
RelationshipUpsertRequest and the new PUT, then migrate every caller:

- RelationshipDateField (mirrors PersonLifeDateField: DAY/MONTH/YEAR, 44px
  targets, labelled, semantic dark-mode tokens, relation_* i18n keys).
- AddRelationshipForm is now upsert-capable: an optional `relationship` prop
  pre-fills type, person, both dates+precision and notes; posts to
  ?/updateRelationship (else ?/addRelationship); the submit control disables and
  shows a progress spinner while a request is in flight (REQ-019); notes textarea
  (<=2000).
- RelationshipChip gains an accessible Edit affordance (canWrite + onEdit);
  StammbaumCard wires it, formats the date range via formatRelationshipDateRange,
  and sorts by fromDate. PersonRelationshipsCard (read view) shows the date range
  and notes; no dates -> no date line.
- persons/[id]/edit/+page.server.ts: updateRelationship action (PUT) + the
  addRelationship action reshaped to date+precision+notes (empty date omits
  precision for coherence).
- Genealogy callers fixed for the dropped year fields: familyForest spouse-order
  and StammbaumConnectors ended-edge dashing now key off fromDate/toDate.
- i18n relation_* form keys in de/en/es.

REQ-004, REQ-014, REQ-015, REQ-016, REQ-019

Refs #837
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/messages/de.json

@@ -1221,6 +1221,16 @@
 	"relation_form_field_from_year": "Von Jahr",
 	"relation_form_field_to_year": "Bis Jahr",
 	"relation_form_year_placeholder": "z.B. 1920",
+	"relation_label_from_date": "Beginn (Datum)",
+	"relation_label_to_date": "Ende (Datum)",
+	"relation_label_date_precision": "Genauigkeit",
+	"relation_precision_day": "Genaues Datum (Tag)",
+	"relation_precision_month": "Monat bekannt",
+	"relation_precision_year": "Nur Jahreszahl",
+	"relation_label_notes": "Notizen",
+	"relation_notes_placeholder": "Optionaler Hinweis zu dieser Beziehung",
+	"relation_date_placeholder_hint": "Leer lassen, wenn unbekannt",
+	"relation_edit": "Beziehung bearbeiten",
 	"person_relationships_heading": "Beziehungen",
 	"person_relationships_empty": "Noch keine Beziehungen bekannt.",
 	"timeline_aria_label": "Zeitachse Dokumentdichte",