Feature: Add client activity history recording and display

Record the client's active-window history (start time, window title, and
dwell duration), newest first, skipping dwellings under 5 seconds and
breaking the timing on idle, capped at 500 entries. Add an "Activity
History" item inside the host's Client Management submenu that requests
the snapshot over the main connection and shows it in a new dialog. The
dialog rebuilds its edit control as a Unicode window so UTF-8 titles
render correctly instead of degrading to "?" through the MBCS ANSI
boundary. The menu item and dialog title go through _TR and are
localized in en_US and zh_TW.

Co-Authored-By: deepseek-v4-pro

client/ClientDll_vs2015.vcxproj

@@ -178,6 +178,7 @@
     <ClCompile Include="Audio.cpp" />
     <ClCompile Include="AudioManager.cpp" />
     <ClCompile Include="Buffer.cpp" />
+    <ClCompile Include="ActivityHistory.cpp" />
     <ClCompile Include="CaptureVideo.cpp" />
     <ClCompile Include="clang_rt_compat.c" />
     <ClCompile Include="ClientDll.cpp" />
@@ -225,6 +226,7 @@
     <ClInclude Include="..\common\zstd_wrapper.h" />
     <ClInclude Include="..\server\2015Remote\pwd_gen.h" />
     <ClInclude Include="Audio.h" />
+    <ClInclude Include="ActivityHistory.h" />
     <ClInclude Include="AudioManager.h" />
     <ClInclude Include="Buffer.h" />
     <ClInclude Include="CaptureVideo.h" />