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>

backend-compliance/tests/test_dsr_routes.py

@@ -697,3 +697,49 @@ class TestDSRTemplates:
         fake_id = str(uuid.uuid4())
         resp = client.get(f"/api/compliance/dsr/templates/{fake_id}/versions", headers=HEADERS)
         assert resp.status_code == 404
+
+
+class TestDSRExport:
+    """Tests for DSR export endpoint."""
+
+    def test_export_csv_empty(self):
+        resp = client.get("/api/compliance/dsr/export?format=csv", headers=HEADERS)
+        assert resp.status_code == 200
+        assert "text/csv" in resp.headers.get("content-type", "")
+        lines = resp.text.strip().split("\n")
+        assert len(lines) == 1  # Header only
+        assert "Referenznummer" in lines[0]
+        assert "Zugewiesen" in lines[0]
+
+    def test_export_csv_with_data(self):
+        # Create a DSR first
+        body = {
+            "request_type": "access",
+            "requester_name": "Export Test",
+            "requester_email": "export@example.de",
+            "source": "email",
+        }
+        create_resp = client.post("/api/compliance/dsr", json=body, headers=HEADERS)
+        assert create_resp.status_code == 200
+
+        resp = client.get("/api/compliance/dsr/export?format=csv", headers=HEADERS)
+        assert resp.status_code == 200
+        lines = resp.text.strip().split("\n")
+        assert len(lines) >= 2  # Header + at least 1 data row
+        # Check data row contains our test data
+        assert "Export Test" in lines[1]
+        assert "export@example.de" in lines[1]
+        assert "access" in lines[1]
+
+    def test_export_json(self):
+        resp = client.get("/api/compliance/dsr/export?format=json", headers=HEADERS)
+        assert resp.status_code == 200
+        data = resp.json()
+        assert "exported_at" in data
+        assert "total" in data
+        assert "requests" in data
+        assert isinstance(data["requests"], list)
+
+    def test_export_invalid_format(self):
+        resp = client.get("/api/compliance/dsr/export?format=xml", headers=HEADERS)
+        assert resp.status_code == 422  # Validation error