feat(wireguard): Implement Reverse MWAN WireGuard v2 Phase 1
WireGuard mesh peers as backup internet uplinks via mwan3 failover.
CLI (wgctl) uplink commands:
- uplink list/add/remove/status/test - Manage peer uplinks
- uplink failover enable/disable - Toggle automatic failover
- uplink priority/offer/withdraw - Priority and mesh advertising
Uplink Library (/usr/lib/wireguard-dashboard/uplink.sh):
- Gossip protocol integration via secubox-p2p
- WireGuard interface creation with IP allocation (172.31.x.x/16)
- mwan3 failover integration
- Connectivity testing and latency measurement
RPCD Backend (9 new methods):
- Read: uplink_status, uplinks
- Write: add_uplink, remove_uplink, test_uplink, offer_uplink,
withdraw_uplink, set_uplink_priority, set_uplink_failover
UCI Config (/etc/config/wireguard_uplink):
- Global settings: auto_failover, failover_threshold, ping_interval
- Provider settings: offering state, bandwidth/latency advertisement
- Per-uplink config: interface, peer_pubkey, endpoint, priority
Phase 2 pending: LuCI dashboard integration
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>