Add Satoshi API

[Bortlesboat]

Adds Satoshi API as an x402 service project.\n\nSatoshi API provides Bitcoin fee intelligence and paid x402 endpoints for AI agents and apps. The docs link points to the first paid-call path so reviewers and agents can verify the x402 flow directly.\n\nProof surfaces:\n- Site: https://bitcoinsapi.com\n- x402 start: https://bitcoinsapi.com/x402/start\n- Discovery: https://bitcoinsapi.com/.well-known/x402\n- Repo: https://github.com/Bortlesboat/bitcoin-api

[Bortlesboat]

May 17, 2026 refresh for review context:

• Satoshi API x402 discovery is live at https://bitcoinsapi.com/.well-known/x402 and https://cdp.bitcoinsapi.com/.well-known/x402.
• The live discovery pack now exposes 19 paid resources and 14 marketplace hero paths, led by the searchable paid briefing alias GET /api/v1/x402/satoshi-bitcoin-fee/fees/briefing.
• New flagship paid SKU: GET /api/v1/fees/briefing, a $0.05 send-or-wait Bitcoin fee briefing bundle for agents.
• Public unpaid checks behave as expected: GET /api/v1/fees/recommended returns 200, while /api/v1/fees/briefing, the searchable briefing alias, and /api/v1/fees/landscape return x402 402 challenges.
• x402 List refresh accepted the current Satoshi API submission on May 17 with success=1&found=8; public directory recrawl is still pending.

The durable listing URLs remain:

• Product: https://bitcoinsapi.com
• Paid host: https://cdp.bitcoinsapi.com
• x402 start guide: https://bitcoinsapi.com/x402/start
• Discovery: https://bitcoinsapi.com/.well-known/x402