Client-facing dashboard

Read https://www.sellermate.ai/api-docs first. It documents the SellerMate Public API: REST over HTTPS, X-API-Key auth, and every tool with its parameters is on that page. Every tool is POST https://api.sellermate.ai/public/v1/tools/{name} with a JSON body.

Build me a client dashboard as a small Next.js app.

- One route per client, /c/[token], where the token maps to an Amazon account id in a server-side config file
- The page shows the last 30 days: spend, sales, ACoS, orders and TACoS at the top, a daily spend and sales chart, a table of the top 10 campaigns by spend, and the top 10 advertised products
- Data comes from get_marketplace_summary, get_campaign_performance and get_advertised_product_performance, fetched on the server, cached for 1 hour
- Put the agency name and logo in the header, nothing SellerMate-branded
- Tokens never appear in client-side code; the API key never leaves the server

Use get_user_context once to list the accounts so I can fill the config file.

Rules:
- My key is in the SELLERMATE_API_KEY environment variable. Send it as the X-API-Key header. Never hard-code it or log it.
- Call get_user_context first and use the accounts it returns. Don't invent account ids.
- Report tools are paginated (page, page_size up to 500, pagination.hasMore). Walk every page.
- On a 429, wait for the Retry-After header and retry. On a 401 or 403, stop and tell me.
- Show me the plan and the code before running anything that writes.

Stack: Next.js App Router, TypeScript, Tailwind, deployable to Vercel. Charts with a lightweight library.