[TASK] Migrate business logic to services

## Feature Description

Business logic should be moved from within the routes and blueprints to separate services. These services should be contained in a `app/services` directory, with files mirroring the blueprints where they would have previously been located.

## Why It's Worth Implementing

Not only does this make our app more consistent with best practices and increase maintainability and testing ease, it also is key to our process of decoupling the frontend and backend. These services will allow us to keep consistent business logic during the intermediate phase where we keep the existing Jinja template serving and also build out the RESTful API.

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## Acceptance Criteria & Solution Requirements
*To close this issue, the following must be met (can be finalized in the comments):*
- [x] 1. Application runs as expected with the new feature integrated seamlessly.
- [x] 2. Code quality metrics are maintained, and linting has been considered in development.
- [x] 3. Testing metrics are maintained, and tests have been updated/added wherever relevant during development.
- [ ] 4. Documentation has been updated to reflect the changes made during development.
- [ ] 5. All business logic has been removed from the `app/blueprints` directory, and is instead kept in the `app/services` directory.