Dynamic Subdomain Proxied to sub path with nginx

sites-available-domain.conf

server {
    listen 80;
    server_name ~^(?<subdomain>.+)\.domain\.com domain.com;

    # Location block for path that threated as assets
    location ~* ^/(?<asset>image|css|js|fonts|@vite|node_modules)/(.*) {
        proxy_pass http://127.0.0.1:3000/$asset/$2;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
    }
    # Location block for assets with specific extensions
    location ~* \.(js|ts|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot|svelte)$ {
        proxy_pass http://127.0.0.1:3000$request_uri;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
    }

    location / {
        set $subdomain_suffix "";

        if ($subdomain) {
            set $subdomain_suffix "/page/$subdomain";
        }

        proxy_pass http://127.0.0.1:3000$subdomain_suffix$request_uri;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
    }
}