feat: Dashboard数据关联修复 + 通知模板优化 + 工单创建页布局

1. Dashboard: stats新增queryStats查询统计, trend API真实工单趋势数据
2. Layout铃铛: 显示真实待审批工单数量
3. 通知模板优化:
   - 创建工单通知: 含申请人+目标实例+库+SQL摘要
   - 审批通过/拒绝通知: 含审批人+目标实例
   - 执行完成/失败通知: 含执行人+目标实例+库
4. 飞书卡片颜色: 创建=turquoise, 审批=blue, 成功=green, 失败=red
5. 钉钉消息: 添加状态emoji标签(🆕✅❌⚠️)
6. TicketCreatePage: 底部操作栏(SQL检测+提交审批)
7. ticket_executor: 移除aiomysql不支持的read_timeout/write_timeout

Tests: 1057 passed, 17 pre-existing failures (notification 35/35 passed)

frontend/src/components/Layout.tsx

@@ -1,3 +1,4 @@
+import { useState, useEffect } from 'react';
 import { Outlet, useLocation, useNavigate } from 'react-router-dom';
 import {
   LayoutDashboard, Database, Server, Zap, Leaf,
@@ -20,6 +21,13 @@ export default function Layout() {
   const location = useLocation();
   const navigate = useNavigate();
   const currentPath = location.pathname.split('/')[1] || 'dashboard';
+  const [pendingCount, setPendingCount] = useState(0);
+
+  useEffect(() => {
+    import('@/api/request').then(m => m.default.get('/dashboard/stats'))
+      .then((data: any) => setPendingCount(data?.ticket_pending ?? 0))
+      .catch(() => {});
+  }, [location.pathname]);
 
   const getPageTitle = () => {
     const item = visibleMenuItems.find(m => m.id === currentPath);
@@ -95,9 +103,14 @@ export default function Layout() {
             >
               {theme === 'dark' ? <Sun className="w-4 h-4" /> : <Moon className="w-4 h-4" />}
             </button>
-            <button className="w-8 h-8 rounded-lg flex items-center justify-center text-[var(--dg-text-muted)] hover:bg-[var(--dg-bg-hover)] transition-colors relative">
+            <button onClick={() => navigate('/tickets')}
+              className="w-8 h-8 rounded-lg flex items-center justify-center text-[var(--dg-text-muted)] hover:bg-[var(--dg-bg-hover)] transition-colors relative">
               <Bell className="w-4 h-4" />
-              <span className="absolute top-1 right-1 w-1.5 h-1.5 bg-red-500 rounded-full" />
+              {pendingCount > 0 && (
+                <span className="absolute -top-0.5 -right-0.5 min-w-[16px] h-4 px-1 bg-red-500 rounded-full text-[10px] text-white font-bold flex items-center justify-center">
+                  {pendingCount > 99 ? '99+' : pendingCount}
+                </span>
+              )}
             </button>
             <div className="w-px h-5 bg-[var(--dg-border)] mx-1" />
             <div className="flex items-center gap-2 pl-1">