GitLab CI/CD, From Zero

Pipelines defined in .gitlab-ci.yml: stages, jobs, and runners that build, test, and deploy on every push - with artifacts, caching, and environments.

1. Phase 1: The Mental Model - One File, A Pipeline, A Machine
2. Phase 2: The Everyday Core - Artifacts, Cache, and Rules
3. Phase 3: Production Reality - Environments, Gates, and Secrets