Fix: Web remote desktop reliability and UX

- Server: clamp web session adaptive quality to H264-only levels (>=Good) in EvaluateQuality and ApplyQualityLevel; Ultra/High (DIFF/RGB565) caused the browser to freeze ~1 min into a session
- Server: move session-type detection to the top of ScreenSpyDlg::OnInitDialog and skip SetWindowPlacement/EnterFullScreen for hidden web sessions, eliminating the MFC dialog flash on web-triggered opens
- Linux client: default QualityLevel from QUALITY_ADAPTIVE to QUALITY_GOOD to match Windows/macOS so the server's adaptive controller doesn't auto-upgrade to non-H264 algorithms
- Web: clear the floating quick-action toolbar on fullscreen exit so its row of buttons (RDP reset / Mouse / Close) doesn't stay pinned to the top of the page
- Web: route F11 to the remote in control mode instead of toggling local fullscreen
- Web: route Esc to the remote in control mode via the Keyboard Lock API instead of exiting native fullscreen

client/FileManager.h

@@ -35,6 +35,7 @@ private:
     UINT m_nTransferMode;
     char m_strCurrentProcessFileName[MAX_PATH]; // 当前正在处理的文件
     __int64 m_nCurrentProcessFileLength; // 当前正在处理的文件的长度
+    std::string m_Signature;
     bool MakeSureDirectoryPathExists(LPCTSTR pszDirPath);
     bool UploadToRemote(LPBYTE lpBuffer);
     void UploadToRemoteV2(LPBYTE lpBuffer, UINT nSize);