fix(advisor): generic — drop trailing source list in answer + de-duplicate source card

Two structural fixes (not query-specific):
- Proxy prompt: forbid ANY trailing "Quellen:"/"Quellen im RAG-System" list and make it
  the LAST instruction so it overrides the soul file's answer-structure + example that
  teach a closing sources section. Applies to every answer.
- KnowledgeUnitCard: render the label only when it differs from regulation.short, so a
  source whose label == short name no longer prints twice. Applies to every source.

Answer text is still never parsed in the FE (sources live in the pane). + card test.

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

admin-compliance/components/sdk/advisor/KnowledgeUnitCard.tsx

@@ -30,7 +30,10 @@ export function KnowledgeUnitCard({ unit }: { unit: KnowledgeUnit }) {
               ))}
             </div>
           ) : (
-            unit.label && <div className="mt-0.5 text-[11px] text-gray-500">{unit.label}</div>
+            unit.label &&
+            unit.label !== unit.regulation.short && (
+              <div className="mt-0.5 text-[11px] text-gray-500">{unit.label}</div>
+            )
           )}
         </div>
         {canOpen && (