feat: implement team analytics
Description
Added a cache-safe Team Analytics module to aggregate team-level statistics including commits, merge requests, issues, projects, and groups.
Includes:
- Aggregated team commit, MR, issue, project, and group data
- Member-wise contribution counts
- Date range filtering utility
- Team-level statistics summary calculation
- Proper timezone handling (Asia/Kolkata)
Designed with modular structure and clean separation of concerns to support scalable team analytics features.