feat: add Gitea Actions runner on private compute

Adds a private runner server on the Hetzner private network with NAT
through the gitea server for outbound internet access. Includes
Terraform resources, Ansible playbooks, and iptables forwarding rules.

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

terraform/variables.tf

@@ -5,6 +5,12 @@ locals {
 
   domain    = "maximhutz.com"
   subdomain = "git"
+
+  network_zone = "eu-central"
+  network_cidr = "10.0.0.0/16"
+  subnet_cidr  = "10.0.1.0/24"
+  server_ip    = "10.0.1.2"
+  runner_ip    = "10.0.1.3"
 }
 
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