Feature/contracts 09 contract cancellation path

[KingFRANKHOOD]

What This PR Does Closes #59

Implements a secure contract cancellation path for the escrow contract, including:

1. Cancellation support before funding and under agreed funded/disputed conditions.
2. Strong authorization checks by contract state.
3. Full test coverage for happy paths and failure paths.
4. Security and threat-model documentation updates.
5. Lint/format compliance for clean CI.

Scope

Repository: Talenttrust/Talenttrust-Contracts

Functional Changes

1. Added cancellation lifecycle support in escrow logic.
2. Extended status flow to include Cancelled.
3. Added cancellation reason tracking and cancellation metadata.
4. Added cancel_contract flow with state-specific policy:
   • Created: client or freelancer can cancel.
   • Funded: controlled cancellation paths under defined conditions.
   • Disputed: arbiter-governed cancellation path.
   • Completed/Cancelled: cancellation blocked.
5. Added contract query helper coverage for cancellation validation.

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[KingFRANKHOOD]

@mikewheeleer Please review,

[mikewheeleer]

@KingFRANKHOOD please resolve the conflicts

[KingFRANKHOOD]

@mikewheeleer all conflicts resolved