chore: sentry and nextjs major bumps (#633)

* chore: remove nextjs-config

* build fix

* sentry update

* nextjs update

* feature flags doc

* 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

* no sentry backward compat

* better .env.example

* AUTHENTIK_REFRESH_TOKEN_URL not so required

* accommodate auth system to requiredLogin feature

---------

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

www/app/lib/array.ts

@@ -0,0 +1,12 @@
+export type NonEmptyArray<T> = [T, ...T[]];
+export const isNonEmptyArray = <T>(arr: T[]): arr is NonEmptyArray<T> =>
+  arr.length > 0;
+export const assertNonEmptyArray = <T>(
+  arr: T[],
+  err?: string,
+): NonEmptyArray<T> => {
+  if (isNonEmptyArray(arr)) {
+    return arr;
+  }
+  throw new Error(err ?? "Expected non-empty array");
+};