feat(trading): align option contract schemas

[carlostasada]

What

Aligns option contract, deliverable, and contract-query schemas with the current Trading API specification.

Why

This option-focused extraction from #698 isolates public contract changes and settlement validation for independent review.

Changes

• Adds option contract status, style, type, and settlement enums.
• Adds typed option deliverables and validates delayed-settlement amount rules.
• Aligns option contract response fields and request serialization.
• Documents new public symbols and adds compatibility and route coverage.

Breaking changes

• Option contract deliverables are now typed rather than accepted as arbitrary values.
• Selected fields follow the current API's required/nullability contract.

Testing

• Full suite: 257 passed on Python 3.11.
• Focused option tests: 26 passed.
• Black and warnings-fatal Sphinx build passed.

Desired feedback

Please focus on deliverable settlement validation, field optionality, and exact query serialization.

Checklist

• 323 changed lines, below the split cap
• Full and focused tests pass
• Formatting and documentation build pass
• Public API changes documented

References

• Extracted from feat(trading): align api schemas with current spec - Breaking Changes #698

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