Feature: Add get/set clipboard buttons to remote desktop toolbar

Add two toolbar buttons — get clipboard (letter C) and set clipboard (letter P) —
after the screenshot button and before the minimize button, so clipboard sync stays
reachable in fullscreen mode where the system menu cannot be opened.

The buttons reuse the existing IDM_GET_CLIPBOARD / IDM_SET_CLIPBOARD system-menu
handlers by posting WM_SYSCOMMAND to the parent. The toolbar button count grows
from 16 to 18, and the slide/animation dimensions are widened from 640 to 720.
Letter C/P icons and Simplified-Chinese source strings ("获取剪贴板", "设置剪贴板")
are added, along with English and Traditional-Chinese translations.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/lang/en_US.ini

@@ -231,6 +231,8 @@ RTT=RTT
 放下面=Send Back
 透明度=Opacity
 截图=Capture
+获取剪贴板=Get Clipboard
+设置剪贴板=Set Clipboard
 
 ; ============================================
 ; Settings Dialog