fix(nginx): remove subdomain server block causing redirect loop

The python.anyplot.ai server block was placed before the main server block.
Since server_name _ is not a true catch-all, nginx used the subdomain block
as the default server, causing all requests to redirect to /python/ in a loop.

Remove the block entirely — DNS for the subdomain isn't configured yet.
Add default_server to the main block to prevent this class of bug.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: MarkusNeusinger

app/nginx.conf

@@ -30,15 +30,8 @@ map $http_user_agent $is_bot {
     ~*showyoubot 1;
 }
 
-# Marketing subdomain: python.anyplot.ai → 301 to /python/
 server {
-    listen 8080;
-    server_name python.anyplot.ai;
-    return 301 https://anyplot.ai/python$request_uri;
-}
-
-server {
-    listen 8080;
+    listen 8080 default_server;
     server_name _;
 
     # Use Google DNS for dynamic upstream resolution (prevents startup crash when domain not yet in DNS)