Feature: Disk Usage via df im Dashboard (LXC-kompatibel)

- get_disk_usage() in system_info.py via /usr/bin/df -P
- GET /api/system/disk-usage Endpoint
- getDiskUsage() im API-Client
- Dashboard zeigt Disk Usage Karten mit Balken + Total/Used/Free
  (sichtbar auf LXC wo /proc/diskstats keine Blockgeräte liefert)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/system.py

@@ -168,7 +168,16 @@ async def get_network_traffic():
     return result
 
 
-# ============== DISK I/O ==============
+# ============== DISK USAGE + I/O ==============
+
+@router.get("/disk-usage")
+async def get_disk_usage():
+    """Get filesystem disk usage from df (public)"""
+    result = system_info.get_disk_usage()
+    if "error" in result:
+        raise HTTPException(status_code=500, detail=result["error"])
+    return result
+
 
 @router.get("/diskio")
 async def get_diskio():

backend/services/system_info.py

@@ -429,6 +429,42 @@ def get_all_units() -> Dict[str, Any]:
         return {"error": str(e)}
 
 
+def get_disk_usage() -> Dict[str, Any]:
+    try:
+        result = subprocess.run(
+            ["/usr/bin/df", "-P", "-x", "tmpfs", "-x", "devtmpfs", "-x", "squashfs", "-x", "overlay"],
+            capture_output=True, text=True, timeout=5
+        )
+        if result.returncode != 0:
+            return {"error": result.stderr}
+
+        filesystems = []
+        for line in result.stdout.strip().split("\n")[1:]:
+            parts = line.split()
+            if len(parts) < 6:
+                continue
+            try:
+                total = int(parts[1]) * 1024
+                used = int(parts[2]) * 1024
+                available = int(parts[3]) * 1024
+                capacity = int(parts[4].rstrip("%"))
+                filesystems.append({
+                    "filesystem": parts[0],
+                    "mountpoint": parts[5],
+                    "total": total,
+                    "used": used,
+                    "available": available,
+                    "capacity": capacity,
+                })
+            except (ValueError, IndexError):
+                continue
+
+        return {"filesystems": filesystems}
+    except Exception as e:
+        logger.error(f"Error getting disk usage: {e}")
+        return {"error": str(e)}
+
+
 def get_journal_logs(limit: int = 20) -> Dict[str, Any]:
     try:
         result = subprocess.run(