Add vote datetime to `vote` DB model

### Feature Description

_A clear and concise description of the feature you're requesting._
Add vote datetime field to the vote DB model
https://github.com/CouncilDataProject/cdp-backend/blob/main/cdp_backend/database/models.py#L698

### Use Case

_Please provide a use case to help us understand your request in context._
The front end wants to be able to sort a person's voting record by vote datetime.

### Solution

_Please describe your ideal solution._

### Alternatives

_Please describe any alternatives you've considered, even if you've dismissed them._