Feature: Web remote desktop bidirectional text clipboard sync

Add keyboard-shortcut (Ctrl+C / Ctrl+X / Ctrl+V) text clipboard transfer
between the browser and the remote desktop, reusing the clipboard protocol
that already exists in the native viewer (COMMAND_SCREEN_GET_CLIPBOARD=24,
COMMAND_SCREEN_SET_CLIPBOARD=25, TOKEN_CLIPBOARD_TEXT=118) so the client
needs no change.

Local -> remote: pressing Ctrl+V reads the browser clipboard, pushes it to
the remote clipboard (UTF-8 -> GBK, matching the client's CF_TEXT/ANSI
handling) and then synthesizes a remote Ctrl+V so the pasted text is the
newly delivered one.

Remote -> local: Ctrl+C or Ctrl+X is forwarded to the remote as usual and,
after a short delay, the remote clipboard is pulled back and written to the
browser clipboard for a later local Ctrl+V.

Both the MFC and Go servers get the same three clipboard signaling paths
(clipboard_set, clipboard_get, clipboard_text) so the shared single-page
frontend behaves identically on either backend.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/ScreenSpyDlg.cpp

@@ -1126,6 +1126,10 @@ VOID CScreenSpyDlg::OnReceiveComplete()
     case TOKEN_CLIPBOARD_TEXT: {
         Buffer str = m_ContextObject->InDeCompressedBuffer.GetMyBuffer(1);
         UpdateServerClipboard(str.c_str(), str.length());
+        // 反向回传：远程剪贴板文本（UTF-8）→ Web 客户端
+        if (m_bIsWebSession && WebService().IsRunning()) {
+            WebService().NotifyClipboardText(m_ClientID, std::string(str.c_str(), str.length()));
+        }
         break;
     }
     case TOKEN_BITMAPINFO: {