feat: add datastore view with storage categories, RAID status monitoring, and live recovery tracking

Add scan_datastore_storage() to walk DATASTORE_PATH and categorize media by directory structure (movies/series/anime/kdrama/downloads/other) with size/file counts. Add raid_status() to parse /proc/mdstat and mdadm --detail for RAID level, active/failed devices, and recovery progress. Add /api/datastore endpoint with 15-minute cache for storage scans and live RAID updates. Install mdadm/util-linux/

Dockerfile

@@ -1,6 +1,6 @@
 FROM python:3.13-slim
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends ffmpeg \
+    && apt-get install -y --no-install-recommends ffmpeg mdadm util-linux smartmontools \
     && rm -rf /var/lib/apt/lists/*
 WORKDIR /app
 COPY requirements.txt .