chore(deps): update dependency tzdata to v2026

Author: renovate[bot]

backend/requirements.txt

@@ -47,7 +47,7 @@ starlette==1.3.1
 types-paramiko==4.0.0.20260322
 types-requests==2.33.0.20260327
 typing_extensions==4.15.0
-tzdata==2025.3
+tzdata==2026.3
 urllib3==2.7.0
 uvicorn==0.42.0
 watchfiles==1.1.1