Fix device detection, tree indentation, and hide Single storage type

- Replace findmnt with lsblk for efficient device name detection
- Fix tree indentation to align consistently with status icon text
- Hide '(Single)' label for single disk storage pools
- Device detection returns actual names (nvme0n1, sda) not UUID paths

dashboard/src/ui/widgets/system.rs

@@ -254,9 +254,14 @@ impl SystemWidget {
                 _ => "—% —GB/—GB".to_string(),
             };
             
+            let pool_label = if pool.pool_type.to_lowercase() == "single" {
+                format!("{}:", pool.mount_point)
+            } else {
+                format!("{} ({}):", pool.mount_point, pool.pool_type)
+            };
             let pool_spans = StatusIcons::create_status_spans(
                 pool.status.clone(),
-                &format!("{} ({}):", pool.mount_point, pool.pool_type)
+                &pool_label
             );
             lines.push(Line::from(pool_spans));
 
@@ -280,7 +285,7 @@ impl SystemWidget {
                 };
 
                 let mut drive_spans = vec![
-                    Span::raw(" "),
+                    Span::raw("  "),
                     Span::raw(tree_symbol),
                     Span::raw(" "),
                 ];
@@ -292,7 +297,7 @@ impl SystemWidget {
             if pool.usage_percent.is_some() {
                 let tree_symbol = "└─";
                 let mut usage_spans = vec![
-                    Span::raw(" "),
+                    Span::raw("  "),
                     Span::raw(tree_symbol),
                     Span::raw(" "),
                 ];
@@ -429,7 +434,7 @@ impl Widget for SystemWidget {
         
         let freq_text = self.format_cpu_frequency();
         lines.push(Line::from(vec![
-            Span::raw("└─ "),
+            Span::raw("  └─ "),
             Span::styled(format!("Freq: {}", freq_text), Typography::secondary())
         ]));
 
@@ -443,7 +448,7 @@ impl Widget for SystemWidget {
 
         let tmp_text = self.format_tmp_usage();
         let mut tmp_spans = vec![
-            Span::raw(" └─ "),
+            Span::raw("  └─ "),
         ];
         tmp_spans.extend(StatusIcons::create_status_spans(
             self.memory_status.clone(),