Expose escrow entrypoints and getters on `VeritixToken`

[Ibinola]

Description

escrow.rs is compiled, but its functions are only internal helpers and are not available through the contract interface. That makes the feature inaccessible to downstream clients despite having real logic and tests.

Acceptance Criteria

• VeritixToken exposes create/release/refund escrow entrypoints
• A read-only escrow getter is available through the generated client
• Contract-level tests exercise escrow via the public API instead of direct module calls only

Technical Scope

• Files likely affected: src/contract.rs, src/escrow.rs, src/escrow_test.rs, src/lib.rs
• Modules/contracts involved: VeritixToken, escrow

Dependencies

None

Notes

Keep the internal helpers if they remain useful for dispute integration.