feat(backup): add independent backup panel, configurable policy, and rename support

Extract backup & restore into a standalone AccordionItem in Advanced settings.
Add configurable auto-backup interval (disabled/6h/12h/24h/48h/7d) and retention
count (3-50) via settings. Add per-backup rename with inline editing UI.

src-tauri/src/settings.rs

@@ -245,6 +245,14 @@ pub struct AppSettings {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub webdav_backup: Option<serde_json::Value>,
 
+    // ===== 备份策略设置 =====
+    /// Auto-backup interval in hours (default 24, 0 = disabled)
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub backup_interval_hours: Option<u32>,
+    /// Maximum number of backup files to retain (default 10)
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub backup_retain_count: Option<u32>,
+
     // ===== 终端设置 =====
     /// 首选终端应用（可选，默认使用系统默认终端）
     /// - macOS: "terminal" | "iterm2" | "warp" | "alacritty" | "kitty" | "ghostty"
@@ -289,6 +297,8 @@ impl Default for AppSettings {
             skill_sync_method: SyncMethod::default(),
             webdav_sync: None,
             webdav_backup: None,
+            backup_interval_hours: None,
+            backup_retain_count: None,
             preferred_terminal: None,
         }
     }
@@ -623,6 +633,33 @@ pub fn get_skill_sync_method() -> SyncMethod {
         .skill_sync_method
 }
 
+// ===== 备份策略管理函数 =====
+
+/// Get the effective auto-backup interval in hours (default 24)
+pub fn effective_backup_interval_hours() -> u32 {
+    settings_store()
+        .read()
+        .unwrap_or_else(|e| {
+            log::warn!("设置锁已毒化，使用恢复值: {e}");
+            e.into_inner()
+        })
+        .backup_interval_hours
+        .unwrap_or(24)
+}
+
+/// Get the effective backup retain count (default 10, minimum 1)
+pub fn effective_backup_retain_count() -> usize {
+    settings_store()
+        .read()
+        .unwrap_or_else(|e| {
+            log::warn!("设置锁已毒化，使用恢复值: {e}");
+            e.into_inner()
+        })
+        .backup_retain_count
+        .map(|n| (n as usize).max(1))
+        .unwrap_or(10)
+}
+
 // ===== 终端设置管理函数 =====
 
 /// 获取首选终端应用