Add Gitea Actions runner, ansible-lint CI, vault setup, and fix group_vars layout

- Move group_vars into inventory/ so playbooks can find them (was only
  visible to ad-hoc commands via CWD)
- Add Ansible Vault for sensitive variables (gitea/grafana passwords,
  tokens, db credentials) with vault_password_file outside the repo
- Enable Gitea Actions and deploy act_runner with Docker backend on
  the gitea VM
- Add .gitea/workflows/lint.yml to run ansible-lint on every push
- Set up Gitea → GitHub push mirror (sync_on_commit)
- Fix ansible.cfg stdout_callback for ansible-core 2.20 compatibility
- Add python-psycopg2 to gitea role (required for postgresql modules)
- Add docker to gitea_runner role (required by act_runner at startup)
- Exclude password hashes and VM images from git

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

ansible/ansible.cfg

@@ -4,8 +4,10 @@ remote_user        = adyrem
 private_key_file   = ../keys/homelab_ed25519
 roles_path         = roles
 host_key_checking  = False
-stdout_callback    = yaml
+stdout_callback    = default
+result_format      = yaml
 diff_mode          = True
+vault_password_file = ~/.config/homelab/vault_pass
 
 [privilege_escalation]
 become        = True