test: add boundary coverage and dispute lifecycle documentation

[dubemoyibe-star]

Contract Boundary Tests and Dispute Documentation

This PR improves contract reliability by expanding test coverage around important boundary conditions and documenting the dispute lifecycle.

What's included

Escrow Creation Boundary Tests

• Added tests covering zero amounts.
• Added tests covering maximum supported amounts.
• Added tests for invalid token addresses.
• Verified expected behavior for valid and invalid creation scenarios.

Minimum Bid Update Tests

• Added tests ensuring only administrators can update the minimum bid.
• Added tests verifying that values below MIN_BID_FLOOR are rejected.
• Added coverage for successful admin updates.

Dispute Lifecycle Documentation

• Added docs/DISPUTE.md.
• Documented who can open disputes, who resolves them, and timeout behavior.
• Added links from existing project documentation to improve discoverability.
• Included concrete examples and contributor-focused guidance.

Validation

• Tests are deterministic and run across the existing CI matrix.
• Existing contract behavior is preserved.
• Documentation reflects the current implementation.
• The contract continues to build successfully for the WASM target.

Result

This PR strengthens contract safety through additional boundary tests while making dispute behavior easier for contributors and operators to understand.

Closes #1515
Closes #1529
Closes #1545

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[Baskarayelu]

add boundary coverage and dispute lifecycle documentation — love this — merging 👍