fix(settings): normalize tgCpu on load so a bad value can't block saving (#5091)
The settings page validates the whole AllSetting object before saving, so a
tgCpu value that isn't an integer in 0-100 (left over from an older or corrupt
setting) failed validation with "tgCpu: Invalid input" and blocked saving every
other setting too. Clamp/round tgCpu to a valid integer in the model
constructor, defaulting to 80 when it isn't a finite number.