Refactor server-side code

Before moving forward, the server-side code (`node.js` + `express.js`) should be refactored. Current proposals are to:
- Refactor each route into their own file. This will help with being able to test the code in smaller pieces.
- Export the `getData` function. While one instance will not apply to all routes, a majority of it can be refactored out.

Start by locating the server-side route definitions and the getData function mentioned in the issue, then read how routes currently share that logic. Done means routes are separated into individual files and getData is exported or refactored for reuse, with the smaller pieces testable as intended.

Written by the indexing model from the issue text.