feat: 在前端侧边栏添加 GitHub 仓库链接

- 在侧边栏底部添加 GitHub 图标按钮
- 点击后在新标签页打开项目仓库
- 添加蓝色主题样式，与界面风格统一
- 支持响应式设计，移动端适配

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

static/css/main.css

@@ -163,6 +163,16 @@ input, textarea, select { font-family: inherit; }
   transition: all var(--transition);
 }
 .btn-logout:hover { background: rgba(184,92,56,0.35); color: #FAEBD7; }
+.btn-github {
+  width: 100%; padding: 0.45rem;
+  background: rgba(88,166,255,0.15); border: 1px solid rgba(88,166,255,0.3);
+  border-radius: var(--radius-sm); color: rgba(88,166,255,0.9); font-size: 0.78rem;
+  margin-top: 0.4rem; transition: all var(--transition);
+  display: flex; align-items: center; justify-content: center; gap: 0.5rem;
+  text-decoration: none;
+}
+.btn-github:hover { background: rgba(88,166,255,0.25); color: #58A6FF; }
+.btn-github svg { flex-shrink: 0; }
 .btn-theme {
   width: 100%; padding: 0.45rem;
   background: rgba(255,255,255,0.06); border: 1px solid rgba(255,255,255,0.1);
@@ -851,7 +861,7 @@ tr:hover td { background: rgba(184,92,56,0.04); }
   .nav-item { justify-content: center; padding: 0.7rem; }
   .sidebar-bottom { padding: 0.5rem; }
   .user-chip { justify-content: center; }
-  .btn-logout, .btn-theme { font-size: 0; padding: 0.45rem 0; }
+  .btn-logout, .btn-github, .btn-theme { font-size: 0; padding: 0.45rem 0; }
   .page { padding: 1rem; }
   .groups-column { width: 180px; }
   .accounts-column { width: 240px; }

templates/index.html

@@ -57,6 +57,12 @@
                         <div class="user-chip-role">Outlook 管理</div>
                     </div>
                 </div>
+                <a href="https://github.com/ZeroPointSix/outlookEmailPlus" target="_blank" class="btn-github" title="访问 GitHub 仓库">
+                    <svg width="20" height="20" viewBox="0 0 16 16" fill="currentColor">
+                        <path d="M8 0C3.58 0 0 3.58 0 8c0 3.54 2.29 6.53 5.47 7.59.4.07.55-.17.55-.38 0-.19-.01-.82-.01-1.49-2.01.37-2.53-.49-2.69-.94-.09-.23-.48-.94-.82-1.13-.28-.15-.68-.52-.01-.53.63-.01 1.08.58 1.23.82.72 1.21 1.87.87 2.33.66.07-.52.28-.87.51-1.07-1.78-.2-3.64-.89-3.64-3.95 0-.87.31-1.59.82-2.15-.08-.2-.36-1.02.08-2.12 0 0 .67-.21 2.2.82.64-.18 1.32-.27 2-.27.68 0 1.36.09 2 .27 1.53-1.04 2.2-.82 2.2-.82.44 1.1.16 1.92.08 2.12.51.56.82 1.27.82 2.15 0 3.07-1.87 3.75-3.65 3.95.29.25.54.73.54 1.48 0 1.07-.01 1.93-.01 2.2 0 .21.15.46.55.38A8.013 8.013 0 0016 8c0-4.42-3.58-8-8-8z"/>
+                    </svg>
+                    <span>GitHub</span>
+                </a>
                 <button class="btn-theme" id="themeToggleBtn" onclick="toggleTheme()">☀ 浅色模式</button>
                 <button class="btn-logout" onclick="logout()">退出登录</button>
             </div>