feat: implement contract version and capability discovery for clients

[greatest0fallt1me]

Description:

Expose contract version (e.g., semver string) and optional capability flags (e.g., supports_batch_bet, supports_multi_outcome) so that clients can adapt.

Requirements and Context:

• Must be secure, tested, and documented
• Should add version() -> String (or similar) returning e.g. "1.2.0"
• Optional: add capabilities() -> Vec<Symbol> or struct listing supported features
• Should be read-only and gas-cheap
• Should document versioning policy and capability list
• Must not change business logic

Suggested Execution:

1. Fork the repo and create a branch

   git checkout -b feature/version-capability-discovery

2. Implement changes

   • Write contract: src/lib.rs (add version, optionally capabilities)
   • Add version constant or module; add documentation and NatSpec-style comments

3. Test and commit

   • Run tests; cover version and capabilities return correct values
   • Include test output

Example Commit Message:

feat: implement contract version and capability discovery for clients

Guidelines:

• Minimum 95 percent test coverage
• Clear documentation
• Timeframe: 24 hours