Trust proxy headers for OIDC provider

Set proxy: true so oidc-provider reads X-Forwarded-Proto from Traefik
and generates https:// endpoint URLs in the discovery document.

server/utils/oidc-provider.ts

@@ -23,6 +23,9 @@ export async function getOidcProvider() {
   _provider = new Provider(issuer, {
     adapter: MongoAdapter,
 
+    // Trust X-Forwarded-Proto from Traefik reverse proxy
+    proxy: true,
+
     clients: [
       {
         client_id: process.env.OIDC_CLIENT_ID || "outline-wiki",