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/dashboard.templ

@@ -80,7 +80,9 @@ templ Dashboard(user User) {
                     </div>
                     <div class="flex items-center space-x-4">
                         <a href="/" class="px-3 py-2 text-sm hover:opacity-80" style="color: var(--text-secondary)">Dashboard</a>
-                        <a href="/admin" class="px-3 py-2 text-sm hover:opacity-80" style="color: var(--text-secondary)">Admin</a>
+                        if user.Role == "admin" {
+                            <a href="/admin" class="px-3 py-2 text-sm hover:opacity-80" style="color: var(--text-secondary)">Admin</a>
+                        }
                         <span style="color: var(--text-secondary)">Welcome, { user.Username }!</span>
                         <button onclick="logout()" class="btn-primary px-4 py-2 rounded text-sm">
                             Logout

templates/types.go

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