Restrict RX-7 to allowlisted UserIds (owner + son demo lock)

- GameConfig: RX7AllowedUserIds allowlist + isRX7Allowed/starterCarFor helpers
- ProfileTemplate: no hard-coded starter; granted per-player by UserId
- DataManager: grants RX-7 to allowlisted players, public car to everyone else
- Economy.buyCar + CarManager.spawn: server-side refuse RX-7 for non-allowlisted
- Cars: RX-7 flagged Restricted; client dealership hides it from non-owners
- Gates: stylua clean, selene 0/0, rojo builds

src/client/init.client.luau

@@ -231,6 +231,11 @@ local function rebuildGarage()
 		local owned = ownedIds[car.Id]
 		local equipped = latest.EquippedCarId == car.Id
 
+		-- Hide restricted (allowlist-only) cars from anyone who doesn't own them.
+		if car.Restricted and not owned then
+			continue
+		end
+
 		local row = make("Frame", {
 			Size = UDim2.new(1, 0, 0, 72),
 			BackgroundColor3 = Color3.fromRGB(26, 26, 38),