feat: custom branding (#112)

* add first concept

* remove setup status

* split config page in multiple components

* add custom branding docs

* add test email button

* fix invalid email from header

* add migration

* mount images to host

* update docs

* remove unused endpoint

* run formatter

frontend/src/pages/api/[...all].tsx

@@ -11,7 +11,7 @@ export const config = {
 export default (req: NextApiRequest, res: NextApiResponse) => {
   return httpProxyMiddleware(req, res, {
     headers: {
-      "X-Forwarded-For": req.socket.remoteAddress ?? "",
+      "X-Forwarded-For": req.socket?.remoteAddress ?? "",
     },
     target: "http://localhost:8080",
   });