refactor: 移除WebSocket同步功能及相关代码

feat(theme): 增强侧边栏选中项样式配置
style: 优化主题变量和样式覆盖逻辑
chore: 清理未使用的依赖和配置文件

src/main/db/entities/index.ts

@@ -0,0 +1,5 @@
+export { StudentEntity } from './StudentEntity'
+export { ReasonEntity } from './ReasonEntity'
+export { ScoreEventEntity } from './ScoreEventEntity'
+export { SettlementEntity } from './SettlementEntity'
+export { SettingEntity } from './SettingEntity'