feat(bcn01-lab): onboard BCN01-LAB site and extend module with WAN2 support

- Add sites/BCN01-LAB with full Meraki configuration: VLANs, SSIDs,
  switch ports, 802.1X policy, firewall rules, WAN uplinks and warm spare
- Extend modules/meraki-site to support wan2_* fields in mx_wan_uplinks

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

sites/BCN01-LAB/appliance.tf

@@ -0,0 +1,13 @@
+locals {
+  appliance_ports = [
+    {
+      # Port 7: trunk toward the switch stack
+      # Native VLAN 109 (MANAGEMENT), allows all VLANs
+      port_id       = "7"
+      enabled       = true
+      type          = "trunk"
+      vlan          = 109  # MANAGEMENT — native (untagged) VLAN
+      allowed_vlans = "all"
+    },
+  ]
+}