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/inventory/group_vars/all/vars.yml

@@ -0,0 +1,5 @@
+timezone: Europe/Zurich
+admin_user: adyrem
+admin_ssh_key: "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILdW4rhQFv561bYs8w0/VgR6AFgOLvVsAh6pcjZ/CO2R homelab"
+
+loki_url: "http://10.10.1.137:3100"