[Template] Update x402 template

[AyushBherwani1998]

Description

• Update x402 template to use @metamask/x402 package, and change the network to Base Sepolia.

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Note

Medium Risk
Updates payment scheme wiring and network/facilitator defaults in the x402 server template, which can affect payment enforcement and compatibility. Risk is moderate since changes are confined to a template but touch core payment configuration.

Overview
Updates the Node x402-server template to use @metamask/x402’s x402ExactEvmErc7710ServerScheme instead of the custom local ERC-7710 scheme implementation (and removes src/scheme.ts).

Switches default configuration from Base mainnet to Base Sepolia (eip155:84532) and updates the example FACILITATOR_URL accordingly, alongside dependency updates (adds @metamask/x402/viem, drops @x402/express, and aligns @types/node to v18).

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[jeffsmale90]

@metamask/x402 declares the following peer dependencies:

  "@x402/core": "^2.12.0",
  "@x402/evm": "^2.12.0",
  "viem": "^2.31.4"

I think you'll need to add @x402/evm back in, along with viem (viem is just used to validate the address in the server side, maybe we should remove that dependency 🤔

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[TateLyman]

Ran a static pass on the x402 template update and found one blocking packaging issue.

templates/node/x402-server/src/index.ts still imports the middleware from @x402/express:

import { paymentMiddleware } from "@x402/express";

But the template package now drops @x402/express from templates/node/x402-server/package.json; the final dependency set keeps @metamask/x402, @x402/core, @x402/evm, viem, cors, dotenv, and express, but not @x402/express.

That means a user who generates the x402-server template and runs its own install/build will fail on module resolution. This can also be easy to miss in repo-level checks because this PR changes the root tsconfig.json to exclude ./templates.

Patch direction is either:

• add @x402/express back to the template dependencies, or
• switch the template code to the intended replacement middleware if @metamask/x402 is supposed to own that layer now.

No payment headers, wallets, private endpoints, or live facilitator calls were used for this pass.