fix: 修复应用长时间挂后台后恢复时表格数据永久加载的问题

三层防护：
- MySQL 连接获取时执行 ping 健康检查，死连接自动重连
- macOS Reopen 事件 + 前端 visibilitychange 触发连接刷新
- 前端 Promise.race 超时保护，确保 loading 状态不会超过 60s

apps/desktop/src/stores/queryStore.ts

@@ -708,14 +708,12 @@ export const useQueryStore = defineStore("query", () => {
         clientSessionId: tab.id,
         timeoutSecs: queryTimeoutSecs,
       };
-      const results = await api.executeMulti(
-        tab.connectionId,
-        tab.database,
-        sqlToExecute,
-        tab.schema,
-        executionId,
-        executionOptions,
-      );
+      const frontendTimeoutSecs = Math.max(queryTimeoutSecs * 2, 60);
+      const timeoutError = new Error(`查询超时 (${frontendTimeoutSecs}s)，请检查数据库连接是否正常`);
+      const results = await Promise.race([
+        api.executeMulti(tab.connectionId, tab.database, sqlToExecute, tab.schema, executionId, executionOptions),
+        new Promise<never>((_, reject) => setTimeout(() => reject(timeoutError), frontendTimeoutSecs * 1000)),
+      ]);
       console.info("[DBX][executeTabSql:execute-multi:done]", {
         traceId,
         resultCount: results.length,
@@ -916,6 +914,18 @@ export const useQueryStore = defineStore("query", () => {
     tab.queryEditabilityReason = undefined;
   }
 
+  function notifyConnectionMayBeLost() {
+    const stuck = tabs.value.filter((t) => t.isExecuting);
+    if (stuck.length > 0) {
+      stuck.forEach((t) => {
+        t.isExecuting = false;
+        t.isCancelling = false;
+        t.executionId = undefined;
+        t.result = toErrorResult(new Error("连接可能已断开，请刷新数据重试"));
+      });
+    }
+  }
+
   async function trimResultCache() {
     const inactive = tabs.value.filter((t) => t.id !== activeTabId.value && (t.result || t.results));
     if (inactive.length > MAX_CACHED_RESULTS) {
@@ -964,5 +974,6 @@ export const useQueryStore = defineStore("query", () => {
     cancelTabExecution,
     cancelTabExplain,
     reloadEvictedTab,
+    notifyConnectionMayBeLost,
   };
 });