fix: 调整默认主题色并优化数据库连接配置

1.  将默认主题色从#1171c4更改为#e4393c
2.  在druid配置中开启keepAlive，定期检测空闲连接有效性以应对网络抖动

ruoyi-ui/src/store/modules/settings.js

@@ -6,7 +6,7 @@ const { sideTheme, showSettings, navType, tagsView, tagsViewPersist, tagsIcon, t
 const storageSetting = JSON.parse(localStorage.getItem('layout-setting')) || ''
 const state = {
   title: '',
-  theme: storageSetting.theme || '#1171c4',
+  theme: storageSetting.theme || '#e4393c',
   sideTheme: storageSetting.sideTheme || sideTheme,
   showSettings: showSettings,
   navType: storageSetting.navType === undefined ? navType : storageSetting.navType,