refactor: update Nginx configuration and Docker setup

- Change user directive in Nginx configuration from 'nginx' to 'www-data'.
- Update upstream server configurations in Nginx to use 'localhost' instead of service names.
- Modify Nginx server block to redirect HTTP to a status page instead of Grafana.
- Rename Alertmanager location from '/alertmanager/' to '/alerts/' for consistency.
- Remove deprecated status page configuration and related files.
- Adjust Prometheus configuration to reflect the new Docker network settings.

infra/nginx/conf.d/alertmanager.conf

@@ -2,12 +2,12 @@
 # Proxies requests to Alertmanager
 
 # Alertmanager location
-location /alertmanager/ {
+location /alerts/ {
     # Rate limiting
     limit_req zone=api burst=10 nodelay;
     
     # Remove trailing slash for proxy
-    rewrite ^/alertmanager/(.*)$ /$1 break;
+    rewrite ^/alerts/(.*)$ /$1 break;
     
     # Proxy to Alertmanager
     proxy_pass http://alertmanager_backend;