feat: replace nextjs-config with environment variables (#632)

* chore: remove nextjs-config

* build fix

* update readme

* explicit nextjs env vars + remove feature-unrelated things and obsolete vars from config

* full config removal

* remove force-dynamic from pages

* compile fix

* restore claude-deleted tests

* better .env.example

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Co-authored-by: Igor Loskutov <igor.loskutoff@gmail.com>

www/.gitignore

@@ -40,7 +40,6 @@ next-env.d.ts
 # Sentry Auth Token
 .sentryclirc
 
-config.ts
 
 # openapi logs
 openapi-ts-error-*.log