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/layout.tsx

@@ -6,6 +6,7 @@ import ErrorMessage from "./(errors)/errorMessage";
 import { RecordingConsentProvider } from "./recordingConsentContext";
 import { ErrorBoundary } from "@sentry/nextjs";
 import { Providers } from "./providers";
+import { assertExistsAndNonEmptyString } from "./lib/utils";
 
 const poppins = Poppins({
   subsets: ["latin"],
@@ -20,8 +21,13 @@ export const viewport: Viewport = {
   maximumScale: 1,
 };
 
+const NEXT_PUBLIC_SITE_URL = assertExistsAndNonEmptyString(
+  process.env.NEXT_PUBLIC_SITE_URL,
+  "NEXT_PUBLIC_SITE_URL required",
+);
+
 export const metadata: Metadata = {
-  metadataBase: new URL(process.env.NEXT_PUBLIC_SITE_URL!),
+  metadataBase: new URL(NEXT_PUBLIC_SITE_URL),
   title: {
     template: "%s – Reflector",
     default: "Reflector - AI-Powered Meeting Transcriptions by Monadical",