Replace whale emoji with ASCII 'D' for performance

Emoji rendering in terminals can be very slow, especially when rendered in the hot path (every frame for every docker image). The whale emoji 🐋 was causing significant rendering delays.

Temporary change to ASCII 'D' to test if emoji was the performance issue.

Cargo.lock

@@ -279,7 +279,7 @@ checksum = "a1d728cc89cf3aee9ff92b05e62b19ee65a02b5702cff7d5a377e32c6ae29d8d"
 
 [[package]]
 name = "cm-dashboard"
-version = "0.1.190"
+version = "0.1.191"
 dependencies = [
  "anyhow",
  "chrono",
@@ -301,7 +301,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-agent"
-version = "0.1.190"
+version = "0.1.191"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -324,7 +324,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-shared"
-version = "0.1.190"
+version = "0.1.191"
 dependencies = [
  "chrono",
  "serde",

dashboard/src/ui/widgets/services.rs

@@ -188,9 +188,9 @@ impl ServicesWidget {
                     format!("  {} ", tree_symbol),
                     Typography::tree(),
                 ),
-                // Docker whale icon
+                // Docker icon (simple character for performance)
                 ratatui::text::Span::styled(
-                    "🐋 ".to_string(),
+                    "D ".to_string(),
                     Style::default().fg(Theme::highlight()).bg(Theme::background()),
                 ),
                 // Service name