feat: configure dynamic providers via .env (#1108)

* Use backend API route to fetch dynamic models

# Conflicts:
#	app/components/chat/BaseChat.tsx

* Override ApiKeys if provided in frontend

* Remove obsolete artifact

* Transport api keys from client to server in header

* Cache static provider information

* Restore reading provider settings from cookie

* Reload only a single provider on api key change

* Transport apiKeys and providerSettings via cookies.

While doing this, introduce a simple helper function for cookies

app/routes/api.models.$provider.ts

@@ -0,0 +1,2 @@
+import { loader } from './api.models';
+export { loader };