Fix #668: Chainsaw weapon not damaging light vehicles (e.g. Sultan)

[iManGaaX]

Summary

CAutomobile::VehicleDamage drops an explicitly passed damage intensity that doesn't exceed its minimum of 25.0 - a minimum which is only scaled by the vehicle's mass for collisions; CTaskSimpleFight::FightHitCar passes melee damage scaled by the vehicle's mass (chainsaw: mass * weapon damage * 0.00075), so vehicles lighter than about 1622 kg, such as the Sultan with its 1400 kg, were never damaged by a chainsaw/melee weapon; neither the panels nor the health

Minimum is now dropped for chainsaw/melee weapons, so their damage is always applied; collision damage is untouched (it computes its own, mass scaled minimum) and so is every other weapon (guns and explosions pass a weapon of 49/51)

Closes #668.

Before ->

2026-09-13.05-56-02.mp4

After ->

2026-09-13.06-34-43.mp4

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