Rebases the fork's branch onto current upstream rustdesk/hbb_common main
(6490a86), pulling in 267 upstream commits (security hardening, IPC perm
fixes, file-transfer path-traversal fixes, privacy-mode option, etc).
The local HttpProxyRequest/Response backport is dropped because upstream
now has the same proto messages with the same tag numbers.
Cherry-picks the local "implement app_icon" commit on top, adding the
OPTION_APP_ICON buildin key needed by the customization page.
Sets branch=pro-features in .gitmodules so future
'git submodule update --remote' tracks the right branch.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
mike
2e35d8e45b