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/audit_routes.py

@@ -26,7 +26,7 @@ from ..db.models import (
 )
 from .schemas import (
     CreateAuditSessionRequest, AuditSessionResponse, AuditSessionSummary, AuditSessionDetailResponse,
-    AuditSessionListResponse, SignOffRequest, SignOffResponse,
+    SignOffRequest, SignOffResponse,
     AuditChecklistItem, AuditChecklistResponse, AuditStatistics,
     PaginationMeta,
 )
@@ -164,7 +164,7 @@ async def get_audit_session(
         completion_percentage=session.completion_percentage,
     )
 
-    return AuditSessionDetail(
+    return AuditSessionDetailResponse(
         id=session.id,
         name=session.name,
         description=session.description,