Implement latest updates to NIP-RP

[alejandro-runner]

As per changes submitted to the repository reservation-protocol/ on 10.20.2025:

• duration mandatory for kind:9902 and kind:9904
• Introduced the concept of broker
• Business shall not send attestation token when reservation is made by a broker
• Embed new schema files for validation (see Migrate schema validation from hardcoded to based on files in local project #175)

[alejandro-runner]

• Remove app handlers.
• Flatten 990x kinds.
• Use schema L tags (update also NIP itself)