Initial commit: Ansible playbook for Gitea Act Runner deployment

Automated deployment of act_runner on Ubuntu 20.04+ servers:
- Docker CE installation (DEB822 format)
- Node.js 24.x via NodeSource
- act_runner binary with SHA256 verification
- systemd service with security hardening
- CI: ansible-lint via Gitea Actions

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

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+# Gitea Act Runner - Ansible Playbook
+
+Deploys [Gitea Act Runner](https://docs.gitea.com/usage/actions/act-runner) on Ubuntu 20.04+ servers.
+
+## Usage
+
+```bash
+# Install dependencies
+uv sync
+
+# Configure inventory and vault (see examples)
+ansible-vault create group_vars/all/vault.yml
+
+# Deploy
+uv run ansible-playbook -i inventory/hosts.yml playbook.yml --ask-vault-pass
+```
+
+## References
+
+- [Act Runner Docs](https://docs.gitea.com/usage/actions/act-runner)
+- [Gitea Actions](https://docs.gitea.com/usage/actions/overview)