fix: harden backend production deployment

deploy/nginx/whaletown-admin-v2.conf.example

@@ -0,0 +1,21 @@
+server {
+    listen 80;
+    server_name whaletownadmin.xinghangee.icu;
+
+    root /var/www/whale-town-end-v2/client/dist;
+    index index.html;
+
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+
+    location = /index.html {
+        add_header Cache-Control "no-cache";
+    }
+
+    location ~* \.(?:js|css|png|jpg|jpeg|gif|svg|ico|woff2?)$ {
+        expires 7d;
+        add_header Cache-Control "public, max-age=604800, immutable";
+        try_files $uri =404;
+    }
+}