Retry authentication failures

[dcollinsn]

Have pamac-cli explicitly acquire authorization with Transaction.get_authorization_async() before starting a privileged transaction. Repeat a plain unsuccessful authorization request, but stop when authorization succeeds, the user presses Ctrl-C, or libpamac emits an error with diagnostic details.

While authorization is pending, treat Ctrl-C as cancellation of the entire operation and return status 130. This ensures that losing the terminal agent cannot move the interaction to a GUI agent while the CLI transaction continues.

Resolves #12

[dcollinsn]

Before this patch, I tried pamac reinstall which. When entering an incorrect password, the process immediately aborted.

I built pamac-cli including this patch with meson setup --reconfigure /home/dcollins/pamac-cli/builddir /home/dcollins/pamac-cli --prefix=/usr --sysconfdir=/etc --buildtype=release and installed it with sudo meson install -C /home/dcollins/pamac-cli/builddir.

I then repeated pamac reinstall which.

• Entering the correct password succeeded.
• Entering an incorrect password caused a short delay and then a new password prompt.
• Pressing Ctrl+C aborted the entire transaction and returned me to a zsh prompt.