Don't exit on Github API limit reached

[coolGi69]

When the Github free API limit is reached, Kaon currently just exits.

[2026-03-21T08:05:22] [default] info: This log only represents the most recent run of Kaon!
[2026-03-21T08:05:22] [steam] info: Found Steam: "/home/coolgi/.steam/steam"
[2026-03-21T08:05:22] [heroic] info: Found Heroic: "/home/coolgi/.config/heroic"
[2026-03-21T08:05:22] [itch] info: Itch not found
[2026-03-21T08:05:22] [default] warning: QQmlApplicationEngine failed to load component
[2026-03-21T08:05:22] [default] warning: qrc:/qt/qml/dev/lorendb/kaon/qml/Main.qml: module "kvantum" is not installed
[2026-03-21T08:05:26] [portal2vr] warning: "Attempted to activate nonexistent Portal 2 VR"
[2026-03-21T08:05:26] [uevr] warning: "Attempted to activate nonexistent UEVR"
[2026-03-21T08:05:26] [default] info: Shutting down
[2026-03-21T08:05:26] [vdf] info: Dumping app info to "/home/coolgi/.cache/LorenDB/Kaon/appinfo/"
[2026-03-21T08:05:26] [portal2vr] info: Error while fetching releases: "Error transferring https://api.github.com/repos/Gistix/portal2vr/releases - server replied with status code 403"
[2026-03-21T08:05:26] [uevr] info: Error while fetching releases: "Error transferring https://api.github.com/repos/praydog/UEVR/releases - server replied with status code 403"
[2026-03-21T08:05:26] [uevr] info: Error while fetching releases: "Error transferring https://api.github.com/repos/praydog/UEVR-nightly/releases - server replied with status code 403"

Potentially add checks for this, as well as adding a way for the user to provide their own token.