Add Git repository link to sidebar navigation

- Added Git repository navigation item below Medivault link
- Links to working Headscale setup branch
- Opens in new tab for easy access to project source

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

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

farmq-admin/templates/base.html

@@ -233,6 +233,11 @@
                                 <i class="fas fa-external-link-alt"></i> Medivault
                             </a>
                         </li>
+                        <li class="nav-item">
+                            <a class="nav-link" href="https://git.0bin.in/thug0bin/headscale-tailscale-replacement/src/branch/feature/working-headscale-setup" target="_blank">
+                                <i class="fab fa-git-alt"></i> Git Repository
+                            </a>
+                        </li>
                         <li class="nav-item">
                             <a class="nav-link" href="#" onclick="refreshData()">
                                 <i class="fas fa-sync-alt"></i> 데이터 새로고침