Update version badges from v4.0 to v4.1

- Update all v4.0 badges to v4.1 across templates
- Add cute v4.1 badge under Stegasoo title in navbar

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

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

frontends/web/templates/index.html

@@ -11,7 +11,7 @@
             <div style="margin-bottom: 40px;">
                 <h1 class="display-4 fw-bold mb-2 title-gold">
                     Stegasoo
-                    <span class="badge bg-success fs-6 ms-2">v4.0</span>
+                    <span class="badge bg-success fs-6 ms-2">v4.1</span>
                 </h1>
                 <p class="lead text-muted mb-0">Hide encrypted data in plain sight.</p>
             </div>
@@ -162,7 +162,7 @@
                     <li class="mb-1">
                         <i class="bi bi-broadcast text-success me-2"></i>
                         <strong>Channel keys</strong> for group isolation
-                        <span class="badge bg-info ms-1">v4.0</span>
+                        <span class="badge bg-info ms-1">v4.1</span>
                     </li>
                 </ul>
             </div>