chore(nix): add OIDC app and webfinger redirect for Nextcloud

- Added OIDC app to Nextcloud with specific URL, SHA256, and license configuration for authentication support.
- Configured Nginx to redirect `.well-known/webfinger` to Nextcloud for improved compatibility.
- Updated Nextcloud settings to include `overwrite.cli.url` for proper URL handling.

systems/x86_64-linux/mx/nginx.nix

@@ -1,4 +1,4 @@
-{ pkgs, lib, ... }:
+{ ... }:
 {
   users.users.nginx.extraGroups = [ "acme" ];
   services.nginx = {
@@ -54,6 +54,9 @@
         locations."/stats" = {
           basicAuthFile = "/var/www/hoyer.xyz/stats.htaccess";
         };
+        locations."/.well-known/webfinger" = {
+          return = "307 https://nc.hoyer.xyz/.well-known/webfinger";
+        };
       };
 
       "surfsite.org" = {