feat(dsr): Go DSR deprecated, Python Export-Endpoint, Frontend an Backend-APIs anbinden

- Go: DEPRECATED-Kommentare an allen DSR-Handlern und Routes
- Python: GET /dsr/export?format=csv|json (Semikolon-CSV, 12 Spalten)
- API-Client: 12 neue Funktionen (verify, assign, extend, complete, reject, communications, exception-checks, history)
- Detail-Seite: Alle Actions verdrahtet (keine Coming-soon-Alerts mehr), Communications + Art.17(3)-Checks + Audit-Log live
- Haupt-Seite: CSV-Export-Button im Header
- Tests: 54/54 bestanden (4 neue Export-Tests)

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

admin-compliance/app/sdk/dsr/page.tsx

@@ -808,15 +808,31 @@ export default function DSRPage() {
         explanation={stepInfo.explanation}
         tips={stepInfo.tips}
       >
-        <button
-          onClick={() => setShowCreateModal(true)}
-          className="flex items-center gap-2 px-4 py-2 bg-purple-600 text-white rounded-lg hover:bg-purple-700 transition-colors"
-        >
-          <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 6v6m0 0v6m0-6h6m-6 0H6" />
-          </svg>
-          Anfrage erfassen
-        </button>
+        <div className="flex items-center gap-2">
+          <button
+            onClick={() => {
+              const link = document.createElement('a')
+              link.href = '/api/sdk/v1/compliance/dsr/export?format=csv'
+              link.download = 'dsr_export.csv'
+              link.click()
+            }}
+            className="flex items-center gap-2 px-4 py-2 text-gray-600 bg-gray-100 hover:bg-gray-200 rounded-lg transition-colors"
+          >
+            <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M4 16v1a3 3 0 003 3h10a3 3 0 003-3v-1m-4-4l-4 4m0 0l-4-4m4 4V4" />
+            </svg>
+            CSV Export
+          </button>
+          <button
+            onClick={() => setShowCreateModal(true)}
+            className="flex items-center gap-2 px-4 py-2 bg-purple-600 text-white rounded-lg hover:bg-purple-700 transition-colors"
+          >
+            <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 6v6m0 0v6m0-6h6m-6 0H6" />
+            </svg>
+            Anfrage erfassen
+          </button>
+        </div>
       </StepHeader>
 
       {/* Tab Navigation */}