feat(notification): 重构通知系统，新增同步状态通知配置

[jacksen168sub]

通知系统功能重构：

• 新增 showSyncStatusNotifications 配置项，专门控制同步状态通知
• 将原有的 showNotifications 配置项重命名为常驻通知开关
• 明确区分常驻通知（前台服务通知）和同步状态通知
• 移除 foregroundServiceKeepalive 实验性功能选项
• 简化通知配置，提升功能清晰度

界面与配置优化：

• 在设置界面调整通知相关选项的位置和分组
• 优化通知选项的描述文本，增强用户理解
• 更新通知渠道的名称和显示描述
• 改进设置界面的布局和可读性

服务端逻辑调整：

• 修改服务中的通知逻辑，区分常驻通知和同步状态通知
• 优化通知触发条件判断机制
• 提升通知发送的精准性和相关性
• 增强通知系统的灵活性和可控性

用户体验提升：

• 提供更细粒度的通知控制选项
• 减少不必要的前台服务通知干扰
• 增强同步过程的状态可视性
• 优化用户对系统状态的感知

Notification System Function Refactor:

• Added showSyncStatusNotifications configuration item specifically controlling synchronization status notifications
• Renamed original showNotifications configuration item to persistent notification switch
• Clearly distinguished between persistent notifications (foreground service notifications) and sync status notifications
• Removed foregroundServiceKeepalive experimental feature option
• Simplified notification configuration enhancing function clarity

Interface and Configuration Optimization:

• Adjusted positions and groupings of notification-related options in settings interface
• Optimized description texts of notification options enhancing user understanding
• Updated notification channel names and display descriptions
• Improved layout and readability of settings interface

Server Logic Adjustment:

• Modified notification logic in services distinguishing between persistent and sync status notifications
• Optimized notification trigger condition judgment mechanism
• Enhanced accuracy and relevance of notification sending
• Improved flexibility and controllability of notification system

User Experience Enhancement:

• Provided more granular notification control options
• Reduced unnecessary foreground service notification interference
• Enhanced visibility of synchronization process status
• Optimized user perception of system status