Quaternius weapons, input fixes, sound & path fixes

- Added 6 Quaternius weapon models (Pistol, Revolver, Rifle, Shotgun, P90, SniperRifle)
- Created weapon resource files with balanced stats
- Wired Pistol + Rifle into player.tscn replacing Kenney blasters
- Fixed WASD input (matched input map action names)
- Fixed Escape key toggles mouse capture
- Added Audio autoload singleton
- Fixed broken sound asset paths across all scripts
- Fixed all scene ext_resource text paths (nested under assets/kenney-fps/)
- Fixed all .import source_file paths
- Deleted stale .import files (will be regenerated by editor on open)

assets/kenney-fps/objects/enemy.gd

@@ -28,7 +28,7 @@ func _process(delta):
 # Take damage from player
 
 func damage(amount):
-	Audio.play("sounds/enemy_hurt.ogg")
+	Audio.play("assets/kenney-fps/sounds/enemy_hurt.ogg")
 
 	health -= amount
 
@@ -38,7 +38,7 @@ func damage(amount):
 # Destroy the enemy when out of health
 
 func destroy():
-	Audio.play("sounds/enemy_destroy.ogg")
+	Audio.play("assets/kenney-fps/sounds/enemy_destroy.ogg")
 
 	destroyed = true
 	queue_free()
@@ -63,6 +63,6 @@ func _on_timer_timeout():
 			muzzle_b.play("default")
 			muzzle_b.rotation_degrees.z = randf_range(-45, 45)
 
-			Audio.play("sounds/enemy_attack.ogg")
+			Audio.play("assets/kenney-fps/sounds/enemy_attack.ogg")
 
 			collider.damage(5)  # Apply damage to player