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

Dockerfile

@@ -1,16 +1,39 @@
+# ---- Stage 1: Build frontend ----
+FROM node:22-alpine AS frontend-build
+WORKDIR /app/frontend
+COPY frontend/package.json frontend/package-lock.json* ./
+RUN npm ci
+COPY frontend/ ./
+RUN npm run build
+# Output: /app/static/
+
+# ---- Stage 2: Production runtime ----
 FROM python:3.13-slim
 
-RUN apt-get update && \
-    apt-get install -y --no-install-recommends smartmontools sg3-utils && \
-    rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    smartmontools \
+    sg3-utils \
+    lsscsi \
+    util-linux \
+    zfsutils-linux \
+    && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app
 
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
 
-COPY . .
+COPY main.py .
+COPY routers/ routers/
+COPY services/ services/
+COPY models/ models/
+
+# Copy built frontend from stage 1
+COPY --from=frontend-build /app/static/ static/
 
 EXPOSE 8000
 
-CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]
+HEALTHCHECK --interval=30s --timeout=5s --retries=3 \
+    CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8000/api/health')" || exit 1
+
+CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000", "--workers", "2"]