Initial commit: nult - Ansible deployment toolkit

Merged from veridion-gitea and veridion-act-runner-gitea repos.

nult (Null-T) - instant teleportation from Strugatsky's Noon Universe.
Like Null-T, this toolkit instantly deploys infrastructure.

Roles:
- gitea: Gitea server with PostgreSQL (Docker Compose)
- act_runner: Gitea Actions runner

Playbooks:
- gitea.yml: Deploy Gitea server
- act-runner.yml: Deploy Act Runner
- site.yml: Deploy all services

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

roles/act_runner/tasks/docker.yml

@@ -0,0 +1,91 @@
+---
+# =============================================================================
+# Gitea Act Runner - Docker Installation
+# =============================================================================
+#
+# Installs Docker CE following the official Docker documentation:
+# https://docs.docker.com/engine/install/ubuntu/
+#
+# Uses DEB822 format (.sources) as per current Docker documentation.
+#
+# =============================================================================
+
+# Remove old/conflicting Docker packages that may interfere.
+- name: Remove conflicting Docker packages
+  ansible.builtin.apt:
+    name:
+      - docker.io
+      - docker-doc
+      - docker-compose
+      - docker-compose-v2
+      - podman-docker
+      - containerd
+      - runc
+    state: absent
+  failed_when: false
+
+# Install packages required to add Docker's APT repository.
+- name: Install Docker prerequisites
+  ansible.builtin.apt:
+    name:
+      - ca-certificates
+      - curl
+    state: present
+
+# Create directory for APT keyrings.
+- name: Create keyrings directory
+  ansible.builtin.file:
+    path: /etc/apt/keyrings
+    state: directory
+    mode: '0755'
+
+# Download Docker's official GPG key.
+- name: Download Docker GPG key
+  ansible.builtin.get_url:
+    url: https://download.docker.com/linux/ubuntu/gpg
+    dest: /etc/apt/keyrings/docker.asc
+    mode: '0644'
+
+# Get the dpkg architecture for the repository URL.
+- name: Get dpkg architecture
+  ansible.builtin.command: dpkg --print-architecture
+  register: act_runner_dpkg_arch
+  changed_when: false
+
+# Add Docker's APT repository using DEB822 format.
+# This is the modern format recommended by Docker documentation.
+- name: Add Docker APT repository (DEB822 format)
+  ansible.builtin.copy:
+    dest: /etc/apt/sources.list.d/docker.sources
+    mode: '0644'
+    content: |
+      Types: deb
+      URIs: https://download.docker.com/linux/ubuntu
+      Suites: {{ ansible_facts['distribution_release'] }}
+      Components: stable
+      Architectures: {{ act_runner_dpkg_arch.stdout }}
+      Signed-By: /etc/apt/keyrings/docker.asc
+
+# Update apt cache after adding repository.
+- name: Update apt cache
+  ansible.builtin.apt:
+    update_cache: true
+    cache_valid_time: 0  # Force update since we just added a new repo
+
+# Install Docker CE and related packages.
+- name: Install Docker packages
+  ansible.builtin.apt:
+    name:
+      - docker-ce
+      - docker-ce-cli
+      - containerd.io
+      - docker-buildx-plugin
+      - docker-compose-plugin
+    state: present
+
+# Ensure Docker service is running and enabled on boot.
+- name: Ensure Docker service is started and enabled
+  ansible.builtin.systemd:
+    name: docker
+    state: started
+    enabled: true