Item power scores now account for your class

The power number shown on weapons was being calculated without your class passive bonuses. A Signalborn comparing two staves was seeing scores that didn't reflect their 20% magic damage multiplier. A Rogue's dagger scores were off by 22%. A Soldier's were overstated. The comparison was directionally correct but the numbers were wrong.

Power scores now run through the same damage formula the combat engine uses — including class damage multipliers and weapon proficiency bonuses. When a Signalborn picks up a staff, the power score reflects what that staff actually deals in combat for them specifically, not a class-agnostic baseline.