Per-list tables: each .list file gets its own routing table (auto-allocated
200-250) instead of one table per group. Enables BGP redistribution per list.

Gateway metric: "IP metric N" syntax in gateway file. Multiple gateways with
metric get separate route entries (preference-based) instead of ECMP multipath.

Per-gateway failover: route-health.sh removes routes only via dead gateway
in metric groups, keeping fallback routes alive.

Refactored process_routes() into check_list_changed(), resolve_list_file(),
load_list_routes() subfunctions for readability.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>