The GitHub App Setup URL now lands on /auth/github/install, which renders a choice page: bind the installation to a new inst-{id} group or to an existing group the signed-in user owns (owner role re-checked on POST /auth/github/install/bind). Adds an App-JWT helper (getInstallationAccount) to name the auto-created group, audit entries, a console toast, and keeps the installation.created webhook fallback.
