feat(e1): AuditMiddleware als systematisches Safety-Net — alle erfolgreichen POST/PATCH/DELETE erzeugen Audit-Eintrag (Session-basierte user/tenant-Attribuierung, entity_type aus Pfad, source=middleware in changes); schließt Lücke von 349 mutierenden Endpoints in 59 Dateien ohne Audit; Skip-Liste auth/health/errors/audit/external; best-effort; Beweistest test_audit_middleware.py grün (POST ohne explizites log_audit → Audit-Zeile); Regressionssmoke 23/23 grün

app/main.py

@@ -23,7 +23,11 @@ logger = logging.getLogger(__name__)
 from app.config import get_settings  # noqa: E402
 from app.core.db import close_engine, get_engine  # noqa: E402
 from app.core.error_codes import ApiError, build_error_response  # noqa: E402
-from app.core.middleware import CSRFMiddleware, SecurityHeadersMiddleware  # noqa: E402
+from app.core.middleware import (  # noqa: E402
+    AuditMiddleware,
+    CSRFMiddleware,
+    SecurityHeadersMiddleware,
+)
 from app.core.monitoring import record_error, record_request  # noqa: E402
 from app.core.rate_limit import GeneralRateLimitMiddleware  # noqa: E402
 from app.core.resilience import CircuitBreakerMiddleware  # noqa: E402
@@ -472,6 +476,7 @@ def create_app() -> FastAPI:
     )
     app.add_middleware(CSRFMiddleware)
     app.add_middleware(SecurityHeadersMiddleware)
+    app.add_middleware(AuditMiddleware)
     app.add_middleware(GeneralRateLimitMiddleware)
     app.add_middleware(RequestLoggingMiddleware)
     app.add_middleware(CircuitBreakerMiddleware)