New resources

Added 4 new resource classes to src/Resources/AccountManagement/:

• DemoAccount — Create MT4 and MT5 demo accounts on a provisioning profile
• ExpertAdvisor — List, read, update, upload file, and delete expert advisors
• Quota — Get user quota, quota update requests, and request region quota updates
• MtServer — Search known trading servers by MT version

Transaction ID auto-generation

Made transactionId optional on all create methods that require it
(Account::create(), AccountReplica::createReplica(), DemoAccount methods).
A 32-character hex ID is auto-generated via bin2hex(random_bytes(16)) when
none is provided. Users can still pass a custom ID for retry scenarios.

• Account::create() — transactionHeader() now always sends the header
• AccountReplica::createReplica() — same pattern
• DemoAccount::createMT4DemoAccount() / createMT5DemoAccount() — same pattern

MetaApiClient accessor methods

Added demoAccounts(), expertAdvisors(), quotas(), and mtServers()
accessors to MetaApiClient, following the existing pattern.

Tests

• 5 new test files: DemoAccountTest.php, ExpertAdvisorTest.php,
  QuotaTest.php, MtServerTest.php — 14 tests total
• 2 new auto-generation tests in AccountManagementTest.php
• 4 type-check assertions in MetaApiClientTest.php

Documentation

Updated README with new sections for each resource and clarified the
optional transactionId behavior.