Build with v0

Build a Next.js (App Router) stablecoin payments app that uses the
Lumx API. Lumx connects local banking rails to stablecoins so I can
collect, hold, convert, and pay out money in either form.

Rules
- Read LUMX_API_KEY from process.env. It must stay server-side — use
  it from server actions and route handlers only, never in a "use
  client" file.
- Pick the base URL from LUMX_ENV. Default to
  https://api-sandbox.lumx.io. Use https://api.lumx.io when
  LUMX_ENV === "production".
- Send every request with the headers:
    Authorization: Bearer ${LUMX_API_KEY}
    Content-Type: application/json
- On non-2xx responses, surface the Lumx error body and HTTP status.
  Do not retry 4xx.

Server actions / route handlers to build
1. POST /api/customers — calls Lumx POST /customers. Body: type
   ("INDIVIDUAL" or "BUSINESS"), name, taxId, country (ISO-3), email.
   Returns the Lumx customer record including verification.link.
2. POST /api/on-ramp — calls Lumx POST /transactions/on-ramp. Body:
   customerId, currency (ISO-3), amount (string). Returns the
   rail-specific deposit instructions.
3. GET /api/transactions/[id] — calls Lumx GET /transactions/:id and
   returns the transaction's current status and timeline.

UI to build (App Router pages)
- /onboarding: form that submits to the customer server action, then
  renders verification.link as a button the customer can open.
- /on-ramp: form that picks a customer, sets a currency and amount,
  calls the on-ramp action, then renders the returned deposit
  instructions in a clean card layout.

Style: shadcn/ui components, Tailwind, light mode default.

Reference: https://docs.lumx.io

const LUMX_BASE =
  process.env.LUMX_ENV === "production"
    ? "https://api.lumx.io"
    : "https://api-sandbox.lumx.io";

async function lumx(path: string, init?: RequestInit) {
  const res = await fetch(`${LUMX_BASE}${path}`, {
    ...init,
    headers: {
      Authorization: `Bearer ${process.env.LUMX_API_KEY}`,
      "Content-Type": "application/json",
      ...init?.headers,
    },
  });
  if (!res.ok) {
    throw new Error(`Lumx ${res.status}: ${await res.text()}`);
  }
  return res.json();
}

export const createCustomer = (input: {
  type: "INDIVIDUAL" | "BUSINESS";
  name: string;
  taxId: string;
  country: string;
  email: string;
}) => lumx("/customers", { method: "POST", body: JSON.stringify(input) });

export const createOnRamp = (input: {
  customerId: string;
  currency: string;
  amount: string;
}) =>
  lumx("/transactions/on-ramp", {
    method: "POST",
    body: JSON.stringify(input),
  });

export const getTransaction = (id: string) => lumx(`/transactions/${id}`);