Change tree symbols to use secondary text color

Update all tree symbols (└─, ├─) in system and backup widgets to use
Typography::secondary() style instead of raw text for consistent
text coloring throughout the interface.

TODO.md

@@ -10,18 +10,19 @@
 
 ## System panel (agent/dashboard)
 
-use following layput:
+use following layout:
 '''
 NixOS:
-Build: xxxxxx dd/mm/yy H:M:S
-Active users: cm, simon
+Build: xxxxxx
+Agen: xxxxxx
 CPU:
-● Load: 0.02 0.31 0.86 • 3000MHz
+● Load: 0.02 0.31 0.86
+└─ Freq: 3000MHz
 RAM:
 ● Usage: 33% 2.6GB/7.6GB  
-● /tmp: 0% 0B/2.0GB  
+ └─ ● /tmp: 0% 0B/2.0GB
 Storage:
-● root (Single):  
+● /:  
  ├─ ● nvme0n1 T: 40C • W: 4%  
  └─ ● 8% 75.0GB/906.2GB
 '''
@@ -29,14 +30,35 @@ Storage:
 - Add support to show login/active users
 - Add support to show timestamp/version for latest nixos rebuild
 
+## Backup panel (dashboard)
+
+use following layout:
+'''
+Latest backup:  
+● <timestamp>
+└─ Duration: 1.3m
+Disk:
+● Samsung SSD 870 QVO 1TB  
+ ├─ S/N: S5RRNF0W800639Y
+└─ Usage: 50.5GB/915.8GB
+Repos:
+● gitea (4) 5.1GB  
+● immich (4) 45.0GB  
+● kryddorten (4) 67.8MB  
+● mariehall2 (4) 322.7MB
+● nixosbox (4) 5.5MB  
+● unifi (4) 5.7MB  
+● vaultwarden (4) 508kB
+'''
+
 ## Keyboard navigation and scrolling (dashboard)
 
 - Add keyboard navigation between panels "Shift-Tab"
+- Add lower statusbar with dynamic updated shortcuts when switchng between panels
 - Add scrolling support when text do not fit
 
 ## Remote execution (agent/dashboard)
 
-- Add lower statusbar with dynamic updated shortcuts when switchng between panels
 - Add support for send command via dashboard to agent to do nixos rebuid
 - Add support for navigating services in dashboard and trigger start/stop/restart
 - Add support for trigger backup

dashboard/src/ui/widgets/backup.rs

@@ -80,21 +80,6 @@ impl BackupWidget {
     }
 
 
-    /// Format duration for display
-    fn format_duration(&self) -> String {
-        match self.duration_seconds {
-            Some(seconds) => {
-                if seconds >= 3600 {
-                    format!("{:.1}h", seconds as f32 / 3600.0)
-                } else if seconds >= 60 {
-                    format!("{:.1}m", seconds as f32 / 60.0)
-                } else {
-                    format!("{}s", seconds)
-                }
-            }
-            None => "—".to_string(),
-        }
-    }
 
     /// Format timestamp for display
     fn format_last_run(&self) -> String {
@@ -363,7 +348,7 @@ impl Widget for BackupWidget {
         if let Some(duration) = self.duration_seconds {
             let duration_text = self.format_duration(duration);
             lines.push(ratatui::text::Line::from(vec![
-                ratatui::text::Span::raw("  └─ "),
+                ratatui::text::Span::styled("  └─ ", Typography::secondary()),
                 ratatui::text::Span::styled(format!("Duration: {}", duration_text), Typography::secondary())
             ]));
         }
@@ -384,7 +369,7 @@ impl Widget for BackupWidget {
             // Serial number as sub-item
             if let Some(serial) = &self.backup_disk_serial_number {
                 lines.push(ratatui::text::Line::from(vec![
-                    ratatui::text::Span::raw("  ├─ "),
+                    ratatui::text::Span::styled("  ├─ ", Typography::secondary()),
                     ratatui::text::Span::styled(format!("S/N: {}", serial), Typography::secondary())
                 ]));
             }
@@ -394,7 +379,7 @@ impl Widget for BackupWidget {
                 let used_str = Self::format_size_with_proper_units(used);
                 let total_str = Self::format_size_with_proper_units(total);
                 lines.push(ratatui::text::Line::from(vec![
-                    ratatui::text::Span::raw("  └─ "),
+                    ratatui::text::Span::styled("  └─ ", Typography::secondary()),
                     ratatui::text::Span::styled(format!("Usage: {}/{}", used_str, total_str), Typography::secondary())
                 ]));
             }

dashboard/src/ui/widgets/system.rs

@@ -286,7 +286,7 @@ impl SystemWidget {
 
                 let mut drive_spans = vec![
                     Span::raw("  "),
-                    Span::raw(tree_symbol),
+                    Span::styled(tree_symbol, Typography::secondary()),
                     Span::raw(" "),
                 ];
                 drive_spans.extend(StatusIcons::create_status_spans(drive.status.clone(), &drive_text));
@@ -298,7 +298,7 @@ impl SystemWidget {
                 let tree_symbol = "└─";
                 let mut usage_spans = vec![
                     Span::raw("  "),
-                    Span::raw(tree_symbol),
+                    Span::styled(tree_symbol, Typography::secondary()),
                     Span::raw(" "),
                 ];
                 usage_spans.extend(StatusIcons::create_status_spans(pool.status.clone(), &usage_text));
@@ -435,7 +435,7 @@ impl Widget for SystemWidget {
         
         let freq_text = self.format_cpu_frequency();
         lines.push(Line::from(vec![
-            Span::raw("  └─ "),
+            Span::styled("  └─ ", Typography::secondary()),
             Span::styled(format!("Freq: {}", freq_text), Typography::secondary())
         ]));
 
@@ -453,7 +453,7 @@ impl Widget for SystemWidget {
 
         let tmp_text = self.format_tmp_usage();
         let mut tmp_spans = vec![
-            Span::raw("  └─ "),
+            Span::styled("  └─ ", Typography::secondary()),
         ];
         tmp_spans.extend(StatusIcons::create_status_spans(
             self.memory_status.clone(),