Add Phase 3 tutorials with audience targeting (#94)

## Summary
- Create tutorials directory structure with index page
- Add 5 main tutorials targeting different audiences:
  - **what-is-blumeops** (Reader, AI) - High-level orientation
  - **exploring-the-docs** (All) - Navigation guide
  - **ai-assistance-guide** (AI, Owner) - Context for AI-assisted operations
  - **contributing** (Contributor) - First contribution workflow
  - **replicating-blumeops** (Replicator) - Overview for building similar setup
- Add 4 replication sub-tutorials:
  - tailscale-setup, kubernetes-bootstrap, argocd-config, observability-stack
- Update README.md to mark Phase 3 complete
- Add changelog fragment

Each tutorial explicitly identifies its target audiences and links to reference material rather than re-explaining concepts.

## Deployment and Testing
- [x] All pre-commit hooks pass (doc-links validates wiki links)
- [ ] Build docs via workflow to verify rendering
- [ ] Review content for accuracy

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/94

Brewfile

@@ -2,5 +2,6 @@
 brew "actionlint"  # GitHub/Forgejo Actions workflow linter
 brew "argocd"  # ArgoCD CLI for GitOps management
 brew "bat"  # Syntax-highlighted file concatenation
+brew "mise"  # Task runner and toolchain manager
 brew "tea"  # Gitea/Forgejo CLI for forge.ops.eblu.me
 brew "podman"  # Container CLI (uses VM on macOS, for building/pushing images)