feat(providers): add notes field for provider management

- Add notes field to Provider model (backend and frontend)
- Display notes with higher priority than URL in provider card
- Style notes as non-clickable text to differentiate from URLs
- Add notes input field in provider form
- Add i18n support (zh/en) for notes field

src-tauri/src/provider.rs

@@ -22,6 +22,9 @@ pub struct Provider {
     #[serde(skip_serializing_if = "Option::is_none")]
     #[serde(rename = "sortIndex")]
     pub sort_index: Option<usize>,
+    /// 备注信息
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub notes: Option<String>,
     /// 供应商元数据（不写入 live 配置，仅存于 ~/.cc-switch/config.json）
     #[serde(skip_serializing_if = "Option::is_none")]
     pub meta: Option<ProviderMeta>,
@@ -43,6 +46,7 @@ impl Provider {
             category: None,
             created_at: None,
             sort_index: None,
+            notes: None,
             meta: None,
         }
     }