Display disk serial numbers instead of device names

- Add serial_number field to DriveData structure
- Collect serial numbers from SMART data for all drives
- Display truncated serial numbers (last 8 chars) in dashboard
- Fix parity drive label to show status icon before "Parity:"
- Fix mount point label styling to match other labels

agent/src/collectors/disk.rs

@@ -534,6 +534,7 @@ impl DiskCollector {
 
             agent_data.system.storage.drives.push(DriveData {
                 name: drive.name.clone(),
+                serial_number: smart.and_then(|s| s.serial_number.clone()),
                 health: smart.map(|s| s.health.clone()).unwrap_or_else(|| drive.health.clone()),
                 temperature_celsius: smart.and_then(|s| s.temperature_celsius),
                 wear_percent: smart.and_then(|s| s.wear_percent),