fix: properly configure Apache MPM Prefork with dedicated config file

- Create dedicated apache/mpm_prefork.conf to override default MPM settings
- Mount mpm_prefork.conf to /etc/apache2/mods-available/ to properly apply limits
- Remove MPM config from nextcloud.conf (was being ignored)
- Set ServerLimit and MaxRequestWorkers to 400 (up from 150 default)
- Configure optimized worker settings for better concurrency

This fixes the "server reached MaxRequestWorkers" error that was causing
sync failures and 404 errors by properly overriding Apache's default
configuration file instead of trying to set it in conf-enabled.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -8,6 +8,7 @@ services:
     volumes:
       - ./data:/var/www/html
       - ./apache/nextcloud.conf:/etc/apache2/conf-enabled/nextcloud.conf:ro
+      - ./apache/mpm_prefork.conf:/etc/apache2/mods-available/mpm_prefork.conf:ro
       - ./logs/apache:/var/log/apache2
     logging:
       driver: "json-file"