Re-enable preload_app now that we use gevent instead of eventlet

preload_app was incompatible with eventlet on PyPy but should work
with gevent. Workers share the loaded app via copy-on-write after
fork, reducing per-worker memory usage.

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

Author: vthorsteinsson

config/gunicorn_config.py

@@ -10,6 +10,7 @@
 worker_class = "gevent"
 workers = 4
 timeout = 120
+preload_app = True
 max_requests = 1000
 max_requests_jitter = 50