Refactor upgrade state initialization into a shared `refreshUpgradeState()`
method used by both `mount()` and `checkUpdate()`. The method now uses
`version_compare` to validate upgrade availability and clears the
`new_version_available` flag in InstanceSettings when the current version
is already equal to or newer than the latest version, preventing stale
upgrade notifications from persisting after a successful update.
Covers Upgrade Livewire component mount behavior for:
- initializing latest version from cached versions data
- falling back to 0.0.0 when versions cache is unavailable
