Add power infrastructure reference card (#138)

## Summary
- New `power.md` reference card documenting the full power chain: AC grid → Anker SOLIX F2000 battery → CyberPower CP1000PFCLCD UPS → homelab
- Lists all devices on the UPS (indri, sifaka, UniFi Express 7, Starlink)
- Replaced inline UPS entry on indri card with link to the new power card
- Added power card to reference index

Context: power chain was upgraded — the Anker battery station now sits between grid power and the UPS, providing extended runtime for grid outages.

## Test plan
- [x] docs-check-links, docs-check-index, docs-check-filenames all pass

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

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/138

docs/reference/infrastructure/indri.md

@@ -18,7 +18,7 @@ Primary BlumeOps server. Mac Mini M1 (2020).
 | **macOS** | 15.7.3 (Sequoia) |
 | **Tailscale hostname** | `indri.tail8d86e.ts.net` |
 | **Tailscale Tag** | `tag:homelab` |
-| **UPS** | Anker SOLIX F2000 GaNPrime |
+| **Power** | [[power|Battery-backed UPS]] |
 
 ## Services Hosted