Add example client snippets (curl, fetch, axios, x402)

[Miracle656]

Summary

Help developers integrate Lens faster with copy-paste examples for common HTTP clients.

Files

• new docs/clients.md or update README
• examples in examples/ directory

Acceptance criteria

• curl example for free endpoint
• fetch + axios examples
• x402-paid endpoint with @x402/fetch
• GraphQL query example

[Miracle656]

Closing to reopen with improved Stellar Drips Wave formatting.