downgrade next to fix firefox incompatibility (#258)

## Summary

The local html report was broken on firefox. There is some issue caused
by Next.js. I tried many things and finally fixed it by downgrading the
version from 15 to 13.

Other changes in here include removing dynamic exports which have long
been unneeded and were contributing to the firefox issues. Also after
downgrading versions there were other things that broke that have been
updated here.

I'll report the issue with Next.js 15 and hopefully this can be further
investigated so we can upgrade again in the future.

## Details

- Remove most of the dynamic exports
- Downgrade from Next.js 15.3.4 to 13.4.0.
- Fix ensuing issues created by downgrade including eslint.config.js
issues, change next config from .ts to .mjs, add experimental
esmExternals config option, remove cypress lint config globals as they
were breaking.


## Test Plan

- Mostly just need to get all of the checks passing and ensure cypress
tests still function. The app works in firefox now.


---

"I certify that all code in this PR is my own, except as noted below."

## Use of AI

None

Signed-off-by: dalthecow <[email protected]>

Author: DaltheCow

eslint.config.js

@@ -137,8 +137,6 @@ export default tseslint.config(
         project: './tsconfig.cypress.json',
         tsconfigRootDir: __dirname,
       },
-      // FIX: This is the correct way to get globals from the Cypress plugin's recommended config.
-      globals: cypressPlugin.configs.recommended.languageOptions.globals,
     },
     plugins: {
       cypress: cypressPlugin,