The submodule was carrying a local cherry-pick (proto tags 27/28 for
HttpProxyRequest/Response) on top of upstream rustdesk/hbb_common.
That commit (0c49f9a) only existed on the dev machine, so cloning
elsewhere and running `git submodule update` failed with
"upload-pack: not our ref" because github upstream doesn't have it.
Repoint the submodule URL at gitea.cstudio.ch/mike/hbb_common which
hosts the cherry-picked branch (pro-features-httpproxy) and a mirror
of main. Anyone cloning from now on can `git submodule update --init`
without further setup.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>