✨ feat(controller): gracefully handle missing Uptime Kuma configuration

Previously, the uptime status endpoint returned HTTP 400 with
“未配置 Uptime Kuma URL/Slug” when either option was not set, resulting in
frontend error states.

Changes:
• Treat absence of `UptimeKumaUrl` or `UptimeKumaSlug` as a valid scenario.
• Immediately respond with HTTP 200, `success: true`, and an empty `data` array.
• Preserve existing behavior when both options are provided.

This prevents unnecessary error notifications on the dashboard when
Uptime Kuma integration is not configured and improves overall UX.

controller/uptime_kuma.go

@@ -82,18 +82,11 @@ func GetUptimeKumaStatus(c *gin.Context) {
 	slug := common.OptionMap["UptimeKumaSlug"]
 	common.OptionMapRWMutex.RUnlock()
 
-	if uptimeKumaUrl == "" {
-		c.JSON(http.StatusBadRequest, gin.H{
-			"success": false,
-			"message": "未配置 Uptime Kuma URL",
-		})
-		return
-	}
-
-	if slug == "" {
-		c.JSON(http.StatusBadRequest, gin.H{
-			"success": false,
-			"message": "未配置 Uptime Kuma Slug",
+	if uptimeKumaUrl == "" || slug == "" {
+		c.JSON(http.StatusOK, gin.H{
+			"success": true,
+			"message": "",
+			"data":    []MonitorStatus{},
 		})
 		return
 	}