Add React frontend, ZFS pool mapping, and multi-stage Docker build

- Vite + React frontend with dark-themed dashboard, slot grid per
  enclosure, and SMART detail overlay
- ZFS pool membership via zpool status -P
- Multi-stage Dockerfile (Node build + Python runtime)
- Updated docker-compose with network_mode host and healthcheck

.dockerignore

@@ -1,4 +1,8 @@
+frontend/node_modules
+frontend/.vite
+static/
 __pycache__
 *.pyc
 .git
-.venv
+.env
+*.md