fix(tests): compare UUID objects not str in DATEV coverage test

report_service.datev_monthly_report compares user.company_id (uuid.UUID)
against the passed company_id with != — a plain str from the JSON API
response never equals the UUID, so it always looked like a mismatch.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015Ahyx6D3r7G1EuAc42nezn

backend/tests/test_coverage_gaps.py

@@ -445,8 +445,9 @@ async def test_datev_holiday_takes_precedence_over_vacation(
     from app.services.holiday_service import ensure_holidays_for_year
     from app.services.report_service import report_service
 
-    company_id = cov_company["user"]["company_id"]
-    user_id = cov_company["user"]["id"]
+    from uuid import UUID as _UUID
+    company_id = _UUID(cov_company["user"]["company_id"])
+    user_id = _UUID(cov_company["user"]["id"])
 
     r = await client.patch("/api/v1/companies/me", json={"state": "BY"}, headers=cov_headers)
     assert r.status_code == 200, r.text