Add context menus and SFTP transfer progress handling

- Implemented context menu styles in components.css.
- Added SFTP transfer progress queue and related styles in sftp.css.
- Enhanced app.js to handle SFTP transfer progress events.
- Updated sftp.js to manage transfer progress and render the transfer queue.
- Modified terminal.js to include context menu shortcuts.
- Adjusted manager.go to emit SFTP transfer progress events with direction.
- Updated sshclient.go to modify terminal modes for better performance.

frontend/src/js/app.js

@@ -213,9 +213,12 @@
             }
           }
           // Also re-fit to catch any layout changes that occurred while connecting.
+          // Multiple delays help byobu/tmux render correctly after its status
+          // bar initialisation completes.
           const fit = () => this.terminals.fitSession(payload.sessionID);
           setTimeout(fit, 50);
           setTimeout(fit, 300);
+          setTimeout(fit, 800);
         }
       });
 
@@ -319,6 +322,11 @@
         }
       });
 
+      // SFTP transfer progress events
+      window.runtime.EventsOn("session:sftp:progress", (payload) => {
+        this.sftp.handleTransferProgress(payload);
+      });
+
       // Password/passphrase prompt requests from the backend
       window.runtime.EventsOn("session:secret:prompt", async (payload) => {
         try {