Created Comprehensive Tests for Merchant Account Verification

[Ogstevyn]

Merchant Account Verification Tests

Summary

Adds comprehensive tests for the merchant account verification functionality and fixes several bugs discovered across the contract source files during implementation.

Changes

New

• tests/test_merchant_verification.rs — four test cases covering the full verification lifecycle

Fixed

• account.rs — removed duplicate use imports, duplicate is_restricted_account impl, and orphaned publish_account_restricted_event call
• events.rs — added missing #[contractevent] macro on WithdrawalToEvent, removed duplicate AccountRestricted struct, fixed missing closing } on publish_account_restricted_event
• types.rs — removed duplicate Restricted variant in DataKey enum

Test Coverage

Test	Description
test_initial_state_is_unverified	Newly initialized account returns false for is_verified_account
test_successful_verification	Manager can verify account; status updates and AccountVerified event is emitted
test_unauthorized_verification_panics	Non-manager address calling verify_account panics
test_verify_account_is_idempotent	Calling verify_account twice does not panic and status remains verified

Closes

Closes #29