feat(document): edit document date precision, end and raw

Adds the edit-form date-precision controls to WhoWhenSection: a labelled
precision <select> (min 48px touch target for senior authors), a conditionally
revealed end-date field (only for RANGE, announced via aria-live=polite), and
the verbatim raw cell as labelled read-only static text (not a disabled input).
Fields submit as metaDatePrecision/metaDateEnd/metaDateRaw and flow through the
existing PUT form action.

Backend: DocumentService.updateDocument now persists the three DTO fields (they
existed since #671 but were never applied), so the new controls are real, not
decorative — addresses Nora's "a client <select> constrains nothing" note for
the persistence half. Server-side enum/end>=start validation remains #671's
scope.

Refs #666

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java

@@ -378,6 +378,9 @@ public class DocumentService {
         // 1. Einfache Felder Update
         doc.setTitle(dto.getTitle());
         doc.setDocumentDate(dto.getDocumentDate());
+        doc.setMetaDatePrecision(dto.getMetaDatePrecision());
+        doc.setMetaDateEnd(dto.getMetaDateEnd());
+        doc.setMetaDateRaw(dto.getMetaDateRaw());
         doc.setLocation(dto.getLocation());
         doc.setTranscription(dto.getTranscription());
         doc.setSummary(dto.getSummary());