- Renamed TOPO_BGP to TOPO_GROUP with topo_group_id (64bit)
- Added TOPO_GROUPS container (ll_queue group_list) in UTUN_INSTANCE
- Memory pools moved from TOPO_GROUP to TOPO_GROUPS (instance-level)
- Default group: TOPO_GROUP_UTUN = 0x8000000000000000
- topo_groups_get_default() searches by group_id, not just first entry
- All topo_bgp_* renamed to topo_group_*; function signatures updated
- Files: topo_bgp.h/c -> topo_group.h/c