Allow cleartext HTTP requests only in non-production builds

[pkalita-lbl]

Fixes #119

Despite what this issue says, we didn't really need true separate environments as outlined in https://capacitorjs.com/docs/guides/environment-specific-configurations. What's written there would be necessary for controlling things like app IDs or custom URI schemes by environment. For simply enabling/disabling cleartext HTTP requests we just needed to set the cleartext value based on NODE_ENV.

I believe this only affects Android devices, so with VITE_NMDC_SERVER_API_URL=http://127.0.0.1:8000 (with a local nmdc-server instance running) the app should behave normally when running:

npm run sim.android

However it should not work when running:

NODE_ENV=production npm run sim.android

This is also a good reminder that we should explicitly set the NODE_ENV variable when we set up automated builds.

[eecavanna]

Looks good to me.

I consider this one of the benefits of using a .ts (or .js) file for configuration, rather than a .json file—we can include expressions (i.e. dynamic values) and comments.