CarBody: sculpted per-car visual body kits (cars-first priority)

- New src/server/CarBody.luau: wedge noses, raked glass, pop-up lights (RX-7),
  spoilers (lip/wing/GT), tail styles, exhaust tips, underglow, accent neon,
  alloy rims. All parts Massless+welded: zero physics impact.
- CarManager: replaced the old glass-cube cabin with CarBody.build().

src/server/CarManager.luau

@@ -29,6 +29,7 @@ local Cars = require(Shared.Cars)
 local Chassis = require(Shared.Chassis)
 local GameConfig = require(Shared.GameConfig)
 local DataManager = require(script.Parent.DataManager)
+local CarBody = require(script.Parent.CarBody)
 
 type Car = Cars.Car
 type Tuning = Chassis.Tuning
@@ -208,20 +209,9 @@ local function buildCarModel(car: Car, tuning: Tuning): Model
 	ballastWeld.Part1 = ballast
 	ballastWeld.Parent = body
 
-	-- Cabin (visual only) -------------------------------------------------------
-	local cabin = makePart({
-		Name = "Cabin",
-		Size = Vector3.new(5, 1.6, 5),
-		CFrame = origin * CFrame.new(0, 1.5, 0.5),
-		Color = Color3.new(car.Color[1] * 0.7, car.Color[2] * 0.7, car.Color[3] * 0.7),
-		Material = Enum.Material.Glass,
-		CanCollide = false,
-		Parent = model,
-	})
-	local cabinWeld = Instance.new("WeldConstraint")
-	cabinWeld.Part0 = body
-	cabinWeld.Part1 = cabin
-	cabinWeld.Parent = body
+	-- Visual bodywork (nose, glass, spoilers, lights, underglow, rims) is added
+	-- by CarBody.build() after assembly. All CarBody parts are Massless, so
+	-- they never alter the chassis physics.
 
 	-- Seat: input device only (Throttle/Steer). It drives nothing directly. -----
 	local seat = Instance.new("VehicleSeat")
@@ -247,6 +237,9 @@ local function buildCarModel(car: Car, tuning: Tuning): Model
 		end
 	end
 
+	-- Sculpted visual body kit (per-car styling; all parts Massless + welded)
+	CarBody.build(model, body, car)
+
 	model.PrimaryPart = body
 	return model
 end