feat: Control-Detail Provenance + Atomare Controls Seite

Backend: provenance endpoint (obligations, doc refs, merged duplicates,
regulations summary) + atomic-stats aggregation endpoint.
Frontend: ControlDetail mit Provenance-Sektionen, klickbare Navigation,
neue /sdk/atomic-controls Seite mit Stats-Bar und gefilterer Liste.

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

admin-compliance/app/sdk/control-library/page.tsx

@@ -463,6 +463,16 @@ export default function ControlLibraryPage() {
             onDelete={handleDelete}
             onReview={handleReview}
             onRefresh={fullReload}
+            onNavigateToControl={async (controlId: string) => {
+              try {
+                const res = await fetch(`${BACKEND_URL}?endpoint=control&id=${controlId}`)
+                if (res.ok) {
+                  const data = await res.json()
+                  setSelectedControl(data)
+                  setMode('detail')
+                }
+              } catch { /* ignore */ }
+            }}
             reviewMode={reviewMode}
             reviewIndex={reviewIndex}
             reviewTotal={reviewItems.length}