Complete Phase 6: documentation cleanup and integration (#97)

## Summary
- Delete `docs/zk/` directory - all useful content migrated to structured docs
- Delete `docs/README.md` - `docs/index.md` is now the documentation root
- Add `devpi` reference card and `use-pypi-proxy` how-to guide
- Add maintenance notes to `indri` reference (sleep prevention, passwordless sudo)
- Add iCloud Photos backup note to `borgmatic` reference
- Rewrite `zk-docs` mise task to prime AI context with key docs instead of legacy cards
- Update `CLAUDE.md` and `README.md` to remove zk references
- Update `exploring-the-docs` with AI context priming section

This completes the Diataxis documentation restructuring. All six phases are now done.

## Deployment and Testing
- [x] Pre-commit hooks pass (including doc-links validator)
- [ ] Build and deploy to docs.ops.eblu.me to verify rendering

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

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/97

docs/reference/infrastructure/indri.md

@@ -32,6 +32,12 @@ Primary BlumeOps server. Mac Mini M1 (2020).
 **Kubernetes (via minikube):**
 - [[apps | All k8s applications]]
 
+## Maintenance Notes
+
+**Sleep prevention:** Uses Amphetamine (App Store) to prevent sleep. If Amphetamine crashes after extended uptime, consider switching to `pmset` or `caffeinate` via ansible.
+
+**Passwordless sudo:** Configured for `erichblume` user (`/etc/sudoers.d/erichblume`) to allow ansible `become: true` without prompts. Acceptable given Tailscale is the trust boundary.
+
 ## Related
 
 - [[routing | Routing]] - Port mappings