feat(ci): add multi-platform CI testing via Docker

Add CI infrastructure that tests the Ansible role on every distro
declared in meta/main.yml (EL 8/9, Debian bullseye/bookworm,
Ubuntu focal/jammy/noble) using Docker containers.

- ci/build_matrix.py: parse meta/main.yml platforms into JSON matrix
- ci/test_playbook.yml: test playbook (state=present + validate)
- ci/Dockerfile.el, ci/Dockerfile.debian: per-family Docker images
- Makefile: orchestrator (make test, make test-<slug>, make lint)
- .gitea/workflows/ci.yml: Gitea Actions with dynamic matrix
- .gitlab-ci.yml: GitLab CI pipeline
- Jenkinsfile: Jenkins pipeline with parallel stages
- .yamllint.yml: linter configuration
- .dockerignore: exclude .git and CI configs from Docker context

.gitea/workflows/ci.yml

@@ -0,0 +1,43 @@
+---
+name: CI
+
+on:
+  push:
+    branches: ["*"]
+  pull_request:
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install linters
+        run: pip install ansible-lint yamllint
+      - name: Lint
+        run: make lint
+
+  matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.build.outputs.matrix }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install PyYAML
+        run: pip install pyyaml
+      - name: Build matrix
+        id: build
+        run: echo "matrix=$(python3 ci/build_matrix.py)" >> "$GITHUB_OUTPUT"
+
+  test:
+    needs: [lint, matrix]
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        include: ${{ fromJson(needs.matrix.outputs.matrix) }}
+      fail-fast: false
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install PyYAML
+        run: pip install pyyaml
+      - name: Test ${{ matrix.slug }}
+        run: make test-${{ matrix.slug }}