feat: Add email configuration and alert system

Introduces SMTP configuration settings and alert definitions to enable automated email notifications.
This includes new types for `SmtpConfig` and `AlertDefinition`, and integrates these into the settings page and mock database.
Adds styling for select elements and scrollbar hiding in the main HTML.
Updates mock database logic to potentially support local development without a backend.

nginx.conf

@@ -1,22 +1 @@
-server {
-    listen 80;
-
-    # Serve i file statici della build React
-    location / {
-        root /usr/share/nginx/html;
-        index index.html index.htm;
-        # Importante per React Router: se non trova il file, serve index.html
-        try_files $uri $uri/ /index.html;
-    }
-
-    # Proxy per le chiamate API verso il container backend
-    location /api/ {
-        # 'backend' è il nome del servizio definito nel docker-compose.yml
-        proxy_pass http://backend:3001;
-        proxy_http_version 1.1;
-        proxy_set_header Upgrade $http_upgrade;
-        proxy_set_header Connection 'upgrade';
-        proxy_set_header Host $host;
-        proxy_cache_bypass $http_upgrade;
-    }
-}
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