- Add parse_timezone_offset() helper to parse timezone strings (UTC+3, Africa/Johannesburg, etc.)
- Add get_date_range_in_timezone() helper to calculate date ranges with proper timezone conversion
- Update reports(), export_reports(), client_report_detail(), match_report_detail(), export_client_report(), and export_match_report() to use timezone-aware date filtering
- Users can now select their timezone and date filters will correctly convert local time boundaries to UTC for database queries