feat: restructure firewall module with provider specifications and module configuration

terraform/.terraform/modules/modules.json

@@ -0,0 +1 @@
+{"Modules":[{"Key":"","Source":"","Dir":"."},{"Key":"prod-firewall","Source":"./modules/firewall","Dir":"modules/firewall"}]}

terraform/main.tf

@@ -0,0 +1,3 @@
+module "prod-firewall" {
+   source = "./modules/firewall"
+}

terraform/modules/firewall/main.tf

@@ -1,3 +1,16 @@
+terraform {
+  required_providers {
+    hcloud = {
+      source = "hetznercloud/hcloud"
+      version = "1.57.0"
+    }
+    netbox = {
+      source = "e-breuninger/netbox"
+      version = "5.0.0"
+    }
+  }
+}
+
 resource "hcloud_firewall" "prod-fw" {
   name = "prod-fw"
   rule {