Add listing: LightningFaucet Headers Echo

[pfergi42]

Relationship disclosure: I contribute to LightningFaucet.

Quality evidence:

• Active Bitcoin and Lightning service with roughly 6,600 users and roughly 1,500 monthly Lightning depositors.
• Custodial LND backend, small team, and support@lightningfaucet.com for contact.
• The listed endpoint returned HTTP 402 with an L402 challenge and a 5-sat invoice during verification on 2026-06-08.
• Canonical site: https://lightningfaucet.com/

Content structure: Added one YAML listing in the existing listing format. No UTM parameters.

Validation: ruby YAML parse passed. npm test passed with 1,949 passing tests and 24 skipped.