fix: remove manual gevent monkey-patch that blocked gunicorn worker boot

Gunicorn's gevent worker (-k gevent) handles monkey-patching internally.
The manual patch_all() in app.py ran in the master process before worker
fork, preventing the worker from booting (no 'Booting worker' log line,
server unreachable).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

start.sh

@@ -123,8 +123,6 @@ if [[ "$HAS_GUNICORN" -eq 1 && "$HAS_GEVENT" -eq 1 ]]; then
     echo "[INTERCEPT] Starting production server (gunicorn + gevent)..."
     echo "[INTERCEPT] Listening on ${HOST}:${PORT}"
 
-    export INTERCEPT_USE_GEVENT=1
-
     GUNICORN_ARGS=(
         -k gevent
         -w 1