Add devpi PyPI caching proxy role for indri (#9)

## Summary
- Add ansible role for devpi-server as a transparent PyPI caching proxy
- LaunchAgent with KeepAlive runs via `mise x -- devpi-server`
- Listens on port 3141, data stored in `~/devpi`
- Health checks added to `indri-services-check` script

## Manual Setup Required (on indri, before provisioning)
1. Add to `~/.config/mise/config.toml`:
   ```toml
   [tools]
   "pipx:devpi-server" = "latest"
   "pipx:devpi-web" = "latest"
   "pipx:devpi-client" = "latest"
   ```
2. Run `mise install`
3. Initialize: `mise x -- devpi-init --serverdir ~/devpi`

## Post-Provisioning
- Set up Tailscale service `pypi` on port 443 → 3141
- Configure client pip.conf with index-url

## Test plan
- [x] Ansible syntax check passes
- [x] Dry-run: `mise run provision-indri -- --check --diff`
- [x] Apply: `mise run provision-indri`
- [x] Health check: `mise run indri-services-check`

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

Reviewed-on: https://forge.tail8d86e.ts.net/eblume/blumeops/pulls/9

ansible/playbooks/indri.yml

@@ -18,3 +18,7 @@
       tags: borgmatic
     - role: forgejo
       tags: forgejo
+    - role: devpi
+      tags: devpi
+    - role: devpi_metrics
+      tags: devpi_metrics