[Feature] Add employees model, fix timestamps, and add common fields

[fivetran-reneeli]

Is there an existing feature request for this?

• I have searched the existing issues

Describe the Feature

This is a FR created retroactively to correspond to a customer-created PR so we can track it internally.

• Employee model: Add an employees staging model to include fields like "Name" and "Supervisor" in downstream models.
• Timestamp Conversion Fix: Cast timestamp fields as dates to prevent timezone conversion issues in reporting tools.
• Field Enrichment: Add commonly used fields to key models

Describe alternatives you've considered

No response

Are you interested in contributing this feature?

• Yes.
• Yes, but I will probably need assistance.
• No.

Anything else?

No response