feat(transactions): add validateContractName and validateContractId f…

[Wutche]

…unctions

Adds validation functions for Stacks contract identifiers. Closes #1804
@janniks

Description

Added two new validation functions for Stacks contract identifiers:

• validateContractName(name) - Validates contract name according to Clarity rules
• validateContractId(contractId) - Validates full contract identifier (address.name)

These functions leverage the existing isClarityName() and validateStacksAddress() for consistent validation.

Breaking change?

None - this adds new exports without modifying existing behavior.

Example

import { validateContractName, validateContractId } from '@stacks/transactions';

validateContractName('my-contract');  // true
validateContractName('123invalid');   // false

validateContractId('SP000000000000000000002Q6VF78.pox');  // true
validateContractId('SP000000000000000000002Q6VF78');      // false (no contract name)

Checklist

• Unit tested updated code paths
• Tagged 1 of @janniks or @zone117x for review