Create a page with error codes

### Request Type

Undocumented existing feature

### What needs to be documented?

There are several different error codes that can potentially be informative:

- In Harper, we identify and distinguish known types or classes following standard best practice of using identifiable Error constructor names. Programmatically, this available in the error.name property. In logs, this appears as ErrorInCamelCase: ... stack trace ...
We should put together a list of known meaningful error constructor names in the page here.

- Node.js error codes. These are available from the error.code property and are “yelled” in logs as ERR_SOME_NODE_ERROR_CODE. We can link to the list of error codes here: [Errors | Node.js v25.1.0 Documentation](https://nodejs.org/dist/latest/docs/api/errors.html#nodejs-error-codes)

- We also report errors from our endpoints using HTTP status codes. We try to follow standards for the appropriate error code (link to HTTP specs).

### Where should this be documented?

_No response_

### Why is this needed?

_No response_

### Existing information

_No response_

### Priority/Impact

Medium - important but not urgent

### Are you planning to fix this issue?

No, just reporting the issue

### First-time contributor support

- [ ] I'm new to contributing and would appreciate guidance on the process
- [ ] I'd like help understanding the project structure
- [ ] I need assistance with setting up the development environment
- [ ] I'm comfortable contributing but new to this project specifically