feat: VLAN in FDB, persist vlan, enrich port-devices with hostname, UI columns

Made-with: Cursor

internal/store/sql/003_scan_port_devices.sql

@@ -4,6 +4,7 @@ create table if not exists scan_port_devices (
   ip inet not null,
   if_index int not null,
   bridge_port int not null default 0,
+  vlan int not null default 0,
   mac text not null,
   learned_ip inet null,
   checked_at timestamptz not null