Escrow Contract Enhancements

[ahmadogo]

This PR introduces two major enhancements to the escrow contract: a governance-controlled pause/unpause mechanism and an automatic refund feature for expired escrows.
closes #566

1. Governance-Controlled Pause/Unpause
   To provide administrators with better control over the contract's lifecycle, we've introduced a pausable state.
   closes fix(escrow): Refund expired escrows when no dispute was opened #567
   Changes:

• New ESCROW_ADMIN Role: A new ESCROW_ADMIN role has been added to access_control.rs to manage the contract's pausable state.
  closes test(escrow): Add fuzz tests for dispute-evidence edge cases #568

• Pause and Unpause Functions: Only accounts with the ESCROW_ADMIN role can call the new pause() and unpause() functions.

• State Guard: The create_escrow_advanced, dispute, and release_funds functions are now protected by a when_not_paused guard, preventing them from being executed when the contract is paused.
  closes feat(escrow): Emit structured events for milestone-state transitions #569

• Events: Paused and Unpaused events are now emitted to allow for off-chain monitoring of the contract's state.

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[nanaf6203-bit]

Escrow hardening is always appreciated @ahmadogo — landed!

[nanaf6203-bit]

@ahmadogo just a heads-up — the recent batch of merges that landed ahead of yours touched some shared surface this PR also lives in (errors/traits around escrow), so this one is now reporting a conflict. The escrow error-model + types work here looks good to me; would you mind rebasing onto current main and pushing it again? I will pick it up as soon as it is clean. 🙏

[nanaf6203-bit]

Escrow enhancements are focused and the access-control trait tweak looks intentional. Cargo.lock refresh is fine. Merging. ✅

[nanaf6203-bit]

🟡 Holding for author coordination. This PR and #698 both modify the same files in escrow (contracts/escrow/src/errors.rs, lib.rs, types.rs, plus Cargo.lock), which prevents a clean automatic merge. The escrow enhancements themselves look solid. Could you rebase onto current main and co-ordinate with the #698 author so both can land cleanly?