Add missing function exports to library files

QA scan found 4 library files with functions that weren't exported,
making them unavailable in subshells and nested calls.

Added export statements for:
- lib/attack-signatures.sh: 3 functions
- lib/http-attack-analyzer.sh: 5 functions
- lib/email-functions.sh: 18 functions
- lib/rate-anomaly-detector.sh: 9 functions

Total: 35 functions now properly exported

This ensures functions are available when libraries are sourced by
scripts that spawn subshells or use process substitution.

lib/rate-anomaly-detector.sh

@@ -246,3 +246,14 @@ start_rate_cleanup_task() {
 
     echo $!  # Return PID of cleanup task
 }
+
+# Export functions for use in subshells
+export -f record_request
+export -f detect_rate_anomaly
+export -f analyze_request_pattern
+export -f cleanup_rate_tracking
+export -f get_current_rate
+export -f is_flooding
+export -f format_rate_anomaly
+export -f init_rate_tracking
+export -f start_rate_cleanup_task