Add Convoy Tracking Web UI Dashboard (hq-vr35)

Complete convoy dashboard feature with real-time status tracking:

- Activity package: LastActivity calculation with color thresholds
  (green <2min, yellow 2-5min, red >5min)
- Web package: Template, handler, fetcher for convoy list
- CLI: `gt dashboard [--port=8080] [--open]` command
- Browser E2E tests with rod (headless Chrome)

Features:
- Real-time convoy status with htmx auto-refresh (30s)
- Progress tracking for each convoy
- Last activity indicator with color coding
- Empty state handling

Supersedes: PRs #55, #57, #58, #65, #66

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/dashboard.go

@@ -76,6 +76,9 @@ func runDashboard(cmd *cobra.Command, args []string) error {
 		Addr:              fmt.Sprintf(":%d", dashboardPort),
 		Handler:           handler,
 		ReadHeaderTimeout: 10 * time.Second,
+		ReadTimeout:       30 * time.Second,
+		WriteTimeout:      60 * time.Second,
+		IdleTimeout:       120 * time.Second,
 	}
 	return server.ListenAndServe()
 }