Addresses feedback on #347 regarding error handling in _getSequelizeConnectionManager. When accessing connectionManager throws (Sequelize v7+) and no fallback is available, the original error was silently swallowed, making misconfiguration harder to debug.

Changes:

• Capture exceptions thrown when accessing this.client.connectionManager
• Rethrow the original error object when both connection manager paths fail
• Preserve existing behavior when no access error occurs

Before:

throw new Error('Sequelize connection manager is not available');
// Original error context lost

After:

if (accessError) {
  throw accessError; // Preserves full error object, stack trace, and all properties
}
throw new Error('Sequelize connection manager is not available');

This approach preserves the complete error context including the stack trace, making debugging significantly easier when misconfiguration occurs.

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