Add Apache ProxyTimeout configuration for SSE support

Created apache-sse-config.conf with required Apache settings to support
long-running SSE connections. Apache's mod_proxy_fcgi has a default
timeout of 30-60 seconds which kills SSE connections prematurely.

The configuration sets ProxyTimeout to 21600 seconds (6 hours) to match
HAProxy's timeout and allow long streaming sessions.

Added note to .htaccess explaining this requirement, as ProxyTimeout
cannot be set in .htaccess and must be configured in the virtual host.

To fix 504 Gateway Timeout errors:
1. Add ProxyTimeout directive to Apache virtual host config
2. Reload Apache
3. Test SSE connection

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

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

server/php/.htaccess

@@ -1,6 +1,11 @@
 # Security settings for Multi-User Transcription Server
 # Compatible with both mod_php and php-fpm
 
+# IMPORTANT: For Server-Sent Events (SSE) to work with php-fpm, you MUST configure
+# Apache's ProxyTimeout in your virtual host configuration. See apache-sse-config.conf
+# for the required settings. Without this, Apache will timeout SSE connections after
+# 30-60 seconds with a 504 Gateway Timeout error.
+
 # Deny access to config file directly (if accessed via URL)
 <Files "config.php">
     Require all denied