feat(vendor-assessment): Pruefprotokoll + Frontend + Sidebar

Phase 4-5: Professional Pruefprotokoll report builder with styled HTML
output (Kopfdaten, Kategorie-Scores, L1/L2 Check-Hierarchie, Findings,
Freigabe-Block). Frontend at /sdk/vendor-assessment with 3-step flow:
DocumentUploader → AssessmentProgress → PruefprotokollView.

Sidebar: "Use-Case Audits" → "Vertragspruefung" renamed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend-compliance/compliance/api/vendor_assessment_routes.py

@@ -26,6 +26,9 @@ from compliance.services.dsi_document_checker import (
 from compliance.services.vendor_assessment_cross_check import (
     cross_check_documents,
 )
+from compliance.services.vendor_assessment_report import (
+    build_pruefprotokoll,
+)
 
 logger = logging.getLogger(__name__)
 
@@ -84,6 +87,7 @@ class AssessmentResult(BaseModel):
     overall_score: int = 0
     category_scores: dict[str, int] = {}
     cross_check_findings: list[dict] = []
+    report_html: str = ""
     checked_at: str = ""
 
 
@@ -320,6 +324,12 @@ async def _run_assessment(assessment_id: str, req: AssessmentRequest):
             checked_at=datetime.now(timezone.utc).isoformat(),
         )
 
+        # 8. Generate Pruefprotokoll HTML
+        try:
+            result.report_html = build_pruefprotokoll(result.model_dump())
+        except Exception as e:
+            logger.warning("Report generation failed: %s", e)
+
         job["status"] = "completed"
         job["progress"] = ""
         job["result"] = result