COMMIT_MESSAGE.txt

feat(contracts): add per-offering metadata storage

Implement feature to allow issuers to attach off-chain metadata references
(IPFS hashes, HTTPS URIs, content hashes) to revenue-sharing offerings.

Changes:
- Add OfferingMetadata DataKey for storing metadata references per (issuer, token)
- Implement set_offering_metadata() with issuer authorization and validation
- Implement get_offering_metadata() for retrieval
- Add EVENT_METADATA_SET and EVENT_METADATA_UPDATED events
- Enforce 256-byte size limit on metadata strings
- Add MetadataTooLarge error code
- Respect freeze and pause mechanisms

Testing:
- Add 22 comprehensive tests covering CRUD, authorization, edge cases, and events
- Test coverage: 95%+ (246 total tests passing)
- Validate IPFS CID, HTTPS URL, and content hash formats
- Test metadata isolation per offering
- Test metadata persistence after issuer transfer
- Verify event emission for set and update operations

Documentation:
- Add inline documentation for metadata constraints
- Document expected off-chain usage patterns
- Include examples for IPFS, HTTPS, and hash-based workflows
- Document 256-byte limit rationale

All tests pass, no clippy warnings, code properly formatted.