fix(quality): Ruff/CVE/TS-Fixes, 104 neue Tests, Complexity-Refactoring

- Ruff: 144 auto-fixes (unused imports, == None → is None), F821/F811/F841 manuell
- CVEs: python-multipart>=0.0.22, weasyprint>=68.0, pillow>=12.1.1, npm audit fix (0 vulns)
- TS: 5 tote Drafting-Engine-Dateien entfernt, allowed-facts/sanitizer/StepHeader/context fixes
- Tests: +104 (ISMS 58, Evidence 18, VVT 14, Generation 14) → 1449 passed
- Refactoring: collect_ci_evidence (F→A), row_to_response (E→A), extract_requirements (E→A)
- Dead Code: pca-platform, 7 Go-Handler, dsr_api.py, duplicate Schemas entfernt

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

backend-compliance/compliance/api/ai_routes.py

@@ -36,7 +36,6 @@ async def list_ai_systems(
     db: Session = Depends(get_db),
 ):
     """List all registered AI systems."""
-    import uuid as _uuid
     query = db.query(AISystemDB)
 
     if classification:
@@ -88,7 +87,6 @@ async def create_ai_system(
 ):
     """Register a new AI system."""
     import uuid as _uuid
-    from datetime import datetime
 
     try:
         cls_enum = AIClassificationEnum(data.classification) if data.classification else AIClassificationEnum.UNCLASSIFIED