# Bug Fix: Disk Discovery JSON Parsing Issue

## Problem

The disk listing endpoint was returning `500 Internal Server Error` with the error:
```
failed to parse lsblk output: json: cannot unmarshal number into Go struct field .blockdevices.size of type string
```

## Root Cause

The `lsblk -J` command returns JSON where the `size` field is a **number**, but the Go struct expected it as a **string**. This caused a JSON unmarshaling error.

## Solution

Updated the struct to accept `size` as `interface{}` and added type handling to parse both string and number formats.

## Changes Made

### File: `backend/internal/storage/disk.go`

1. **Updated struct definition** to accept `size` as `interface{}`:
   ```go
   var lsblkOutput struct {
       BlockDevices []struct {
           Name string      `json:"name"`
           Size interface{} `json:"size"` // Can be string or number
           Type string      `json:"type"`
       } `json:"blockdevices"`
   }
   ```

2. **Updated size parsing logic** to handle both string and number types:
   ```go
   // Parse size (can be string or number)
   var sizeBytes int64
   switch v := device.Size.(type) {
   case string:
       if size, err := strconv.ParseInt(v, 10, 64); err == nil {
           sizeBytes = size
       }
   case float64:
       sizeBytes = int64(v)
   case int64:
       sizeBytes = v
   case int:
       sizeBytes = int64(v)
   }
   disk.SizeBytes = sizeBytes
   ```

## Testing

After this fix, the disk listing endpoint should work correctly:

```bash
curl http://localhost:8080/api/v1/storage/disks \
  -H "Authorization: Bearer $TOKEN"
```

**Expected Response**: `200 OK` with a list of physical disks.

## Impact

- ✅ Disk discovery now works correctly
- ✅ Handles both string and numeric size values from `lsblk`
- ✅ More robust parsing that works with different `lsblk` versions
- ✅ No breaking changes to API response format

## Related Files

- `backend/internal/storage/disk.go` - Disk discovery and parsing logic