feat: add ending_at to Schedule

[devin-ai-integration]

This PR adds an optional ending_at property to the Schedule interfaces in the knock-node SDK.

Changes

• Added ending_at?: string | null to the Schedule interface
• Added ending_at?: string to CreateSchedulesProps interface (which is also inherited by UpdateSchedulesProps)

Implementation Details

• The property is optional and requires no validation in the SDK
• Format follows the same pattern as other date fields (ISO-8601 string)
• No breaking changes to existing functionality

Testing

• Existing tests continue to pass
• No additional tests were needed as the property is optional and follows the same pattern as other date fields

Link to Devin run

https://app.devin.ai/sessions/78a792caa098421fb3045c0423cd7d56

[devin-ai-integration]

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