feat: add switch stack port config with dynamic serial resolution

- Add data source meraki_switch_stacks to resolve member serials by stack name
- Add switch_stack_port_configs variable: specify stack_name + port_range
  instead of individual switch serials
- Terraform applies port_range to ALL members of the stack automatically
- Merge switch_port_configs and switch_stack_port_configs into all_ports local
- Add example for bcn01-lab-stack01 (2x48p) in switch.auto.tfvars

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

sites/BCN01-LAB/switch.auto.tfvars

@@ -73,3 +73,42 @@ switch_access_policies = [
 #
 # ]
 switch_port_configs = []
+
+# --- PUERTOS DE STACK ---
+# Terraform resuelve automáticamente los seriales de todos los miembros del stack.
+# El stack_name debe coincidir exactamente con el nombre en Dashboard > Switches > Stacks.
+# Terraform aplicará el mismo port_range a CADA switch del stack (ambos de 48 puertos).
+#
+# Ejemplo para bcn01-lab-stack01 (2x 48 puertos):
+# switch_stack_port_configs = [
+#
+#   # Puertos 1-44: acceso general con 802.1X (PCs, portátiles)
+#   {
+#     stack_name           = "bcn01-lab-stack01"
+#     port_range           = "1-44"
+#     type                 = "access"
+#     vlan                 = 100  # ACCESS - fallback si Okta no devuelve VLAN
+#     access_policy_type   = "Custom access policy"
+#     access_policy_number = 1    # id de la política DOT1X-CORPO
+#   },
+#
+#   # Puertos 45-46: impresoras (VLAN fija, sin 802.1X)
+#   {
+#     stack_name           = "bcn01-lab-stack01"
+#     port_range           = "45-46"
+#     type                 = "access"
+#     vlan                 = 103  # PRINTERS
+#     access_policy_type   = "Open"
+#   },
+#
+#   # Puertos 47-48: APs (VLAN fija, sin 802.1X)
+#   {
+#     stack_name           = "bcn01-lab-stack01"
+#     port_range           = "47-48"
+#     type                 = "access"
+#     vlan                 = 108  # APs
+#     access_policy_type   = "Open"
+#   },
+#
+# ]
+switch_stack_port_configs = []