feat: 7 Analyse-Module auf 100% — Backend-Endpoints, DB-Model, Frontend-Persistenz

Alle 7 Analyse-Module (Requirements → Report) von ~80% auf 100% gebracht:
- Modul 1 (Requirements): POST/DELETE Endpoints + Frontend-Anbindung + Rollback
- Modul 2 (Controls): Evidence-Linking UI mit Validity-Badge
- Modul 3 (Evidence): Pagination (Frontend + Backend)
- Modul 4 (Risk Matrix): Mitigation-UI, Residual Risk, Status-Workflow
- Modul 5 (AI Act): AISystemDB Model, 6 CRUD-Endpoints, Backend-Persistenz
- Modul 6 (Audit Checklist): PDF-Download + Session-History
- Modul 7 (Audit Report): Detail-Seite mit Checklist Sign-Off + Navigation

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

backend-compliance/compliance/db/repository.py

@@ -252,6 +252,15 @@ class RequirementRepository:
 
         return items, total
 
+    def delete(self, requirement_id: str) -> bool:
+        """Delete a requirement."""
+        requirement = self.db.query(RequirementDB).filter(RequirementDB.id == requirement_id).first()
+        if not requirement:
+            return False
+        self.db.delete(requirement)
+        self.db.commit()
+        return True
+
     def count(self) -> int:
         """Count all requirements."""
         return self.db.query(func.count(RequirementDB.id)).scalar() or 0