fix: raise PHP-FPM pool to 30 workers to prevent SSE starvation

SSE connections hold a worker for up to 90 s each; the default of 5
children meant the admin UI became unresponsive under normal use.
Mount zzz-pool.conf (loaded after zz-docker.conf) to override only the
pm.* settings without touching daemonize/listen.

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

docker-compose.yml

@@ -9,6 +9,7 @@ services:
     volumes:
       - .:/var/www
       - ./docker/app/php.ini:/usr/local/etc/php/conf.d/app.ini:ro
+      - ./docker/app/zz-fpm-pool.conf:/usr/local/etc/php-fpm.d/zzz-pool.conf:ro
     depends_on:
       postgres:
         condition: service_healthy

docker/app/zz-fpm-pool.conf

@@ -0,0 +1,8 @@
+[www]
+; SSE connections hold a worker for up to 90 s each — raise the pool ceiling
+; so regular requests are not starved.
+pm = dynamic
+pm.max_children = 30
+pm.start_servers = 4
+pm.min_spare_servers = 2
+pm.max_spare_servers = 8