Fix v1 receipt validation

[oathis]

Summary

• reject unsupported receiptVersion values before signature verification
• require required signed fields to be own, non-null values before canonicalization
• enforce minimum v1 top-level field types for requestJson, reasonCodes, and string fields
• add regressions for unsupported receipt versions and null required signed fields omitted from signature bytes

Addresses permission-protocol/deploy-gate#53 and permission-protocol/deploy-gate#54.

Validation

• npm test -- --run
• npm run build