GPTZero-o rebranding

The whole repository must be rebranded from GPTZero-V to GPTZero-o. I want it to be a media content authenticity toolkit and platform expanding to audio and video, outside of imagery.

This means that every reference of GPTZero-V in the code base, docs, management should become GPTZero-o.

The workspace should take the following naming convention:
- `gptzero-o` is the workspace at the root level
- `gptzero` to `gptzero-o-core`
- `gptzero-api` to `gptzero-o-api`
- `gptzero-sdk` to `gptzero-o-sdk`
- `gptzero-service` to `gptzero-o-service`

The packages should also follow the convention in code, i.e., `gptzero` to `gptzero_o`.

make sure the READMEs and other docs reflect the different scope of the toolkit.

make sure everything runs correctly, unit tests pass and add some integration tests from the SDK / API.

When done, propose a short description and tags for the GitHub About section of the repository. At current, they are:

> A simple attempt at a heuristic GPTZero algorithm for image authenticity verification through metadata analysis

with tags `metadata`, `image-generation`, `heuristic-algorithm`, `content-authenticity`