Add Kunde CRUD with addresses/contacts, delivery edit, and Auftrag sub-nav.

Wire customergroup/entity APIs, Lieferungen detail editing, and Angebot/Bestellung/Ausliefern/Retoure placeholders.

src/components/SectionLayout.jsx

@@ -44,8 +44,13 @@ export default function SectionLayout({ sectionPath }) {
     !isKategorienPath(pathname) &&
     rest &&
     !knownSegments.has(rest);
+  const isKundeDetail =
+    sectionPath === '/kunde' && rest && !knownSegments.has(rest);
+  const isLieferungDetail =
+    sectionPath === '/lieferung' && rest && !knownSegments.has(rest);
+  const isDetail = isArticleDetail || isKundeDetail || isLieferungDetail;
 
-  const pageTitle = isArticleDetail
+  const pageTitle = isDetail
     ? title
     : (activeSub?.label ?? title);