feat: remote file ops, chunked transfers with progress, pause/cancel

- Remove dead Tauri commands/ module
- Add New Folder / Delete / Rename dialogs for remote FS
- Implement chunked upload/download with progress for FTP and SFTP
- Wrap SFTP ops in spawn_blocking
- Add ProgressAction to support cancel/pause mid-transfer
- Update todo.md

src/transfer/queue.rs

@@ -16,6 +16,10 @@ impl TransferQueue {
         self.inner.lock().unwrap().pop_front()
     }
 
+    pub fn get(&self, id: &str) -> Option<TransferTask> {
+        self.inner.lock().unwrap().iter().find(|t| t.id == id).cloned()
+    }
+
     pub fn all(&self) -> Vec<TransferTask> {
         self.inner.lock().unwrap().iter().cloned().collect()
     }