Implement localhost prioritization and status display in dashboard

- Always select localhost as default host at startup
- Order hosts with localhost first, then predefined sequence
- Display hostname status colors in title bar based on metric aggregation
- Add gethostname dependency for localhost detection

Cargo.lock

@@ -255,6 +255,7 @@ dependencies = [
  "clap",
  "cm-dashboard-shared",
  "crossterm",
+ "gethostname",
  "ratatui",
  "serde",
  "serde_json",