Add Firearm Melee Attacks and Bayonets

Allow players to perform close-range melee attacks using their equipped firearm, such as striking an enemy with the stock or muzzle. This would provide a last-resort option during point-blank encounters, including when the weapon is empty. Being struck could briefly interrupt aiming and trigger an appropriate camera or weapon reaction, giving the attacker a momentary advantage without necessarily making standard firearm strikes lethal. Compatible rifles could also support bayonet attachments, providing a more lethal melee option and expanding close-quarters loadout choices.