feat: Add role-based frontend controls

- Update User type to include role field
- Modify dashboard template to conditionally show admin links
- Add protected dashboard route with user context
- Update main.go to serve dashboard with proper authentication

templates/types.go

@@ -4,6 +4,7 @@ type User struct {
 	ID       string
 	Username string
 	Email    string
+	Role     string
 }
 
 type PageData struct {