feat: implement OrganizationEventsResource and UserEventsResource classes

[IamKirbki]

Summary

Split events into separate resources for both organizations and users, following the same pattern used for scheduled resources.

Changes

• Created OrganizationEventsResource in src/core/resources/organizations/events.ts with post() method
• Created UserEventsResource in src/core/resources/users/events.ts with post() method
• Updated OrganizationResource and UserResource to expose events as a nested property
• Removed postEvents methods from the main resource classes

Usage

// Organization events
client.organizations.events.post([...])

// User events
client.users.events.post([...])