Fix 9 MEDIUM hardcoded /var/cpanel paths - ALL MEDIUM ISSUES RESOLVED!

FIXES:
Changed hardcoded /var/cpanel paths to use environment variables with fallbacks:

reference-db.sh:
- Line 255: /var/cpanel/userdata → ${SYS_CPANEL_USERDATA_DIR:-/var/cpanel/userdata}
- Line 265: /var/cpanel/userdata → ${SYS_CPANEL_USERDATA_DIR:-/var/cpanel/userdata}

php-detector.sh:
- Line 69: /var/cpanel/userdata → ${SYS_CPANEL_USERDATA_DIR:-/var/cpanel/userdata}

user-manager.sh:
- Line 44-45: /var/cpanel/users → ${SYS_CPANEL_USERS_DIR:-/var/cpanel/users}
- Line 111: /var/cpanel/users → ${SYS_CPANEL_USERS_DIR:-/var/cpanel/users}

diagnostic-report.sh:
- Line 68: /var/cpanel/users → ${SYS_CPANEL_USERS_DIR:-/var/cpanel/users}

wordpress-cron-manager.sh:
- Line 229-230: /var/cpanel/userdata → ${SYS_CPANEL_USERDATA_DIR:-/var/cpanel/userdata}

IMPACT:
- Paths now configurable via environment variables
- Maintains backward compatibility with default paths
- Better multi-panel support flexibility
- More testable code (can override paths in tests)

QA STATUS:
🎉 ALL MEDIUM ISSUES RESOLVED! 🎉
- CRITICAL: 0 ✓
- HIGH: 0 ✓
- MEDIUM: 0 ✓
- LOW: 11 (remaining)

modules/website/wordpress/wordpress-cron-manager.sh

@@ -226,8 +226,9 @@ case "$choice" in
                 case "$SYS_CONTROL_PANEL" in
                     cpanel)
                         user=$(extract_user_from_path "$site_path")
-                        if [ -f "/var/cpanel/userdata/$user/main" ]; then
-                            domain=$(grep -m1 "^servername:" "/var/cpanel/userdata/$user/main" 2>/dev/null | awk '{print $2}')
+                        local userdata_dir="${SYS_CPANEL_USERDATA_DIR:-/var/cpanel/userdata}"
+                        if [ -f "$userdata_dir/$user/main" ]; then
+                            domain=$(grep -m1 "^servername:" "$userdata_dir/$user/main" 2>/dev/null | awk '{print $2}')
                         fi
                         ;;
                     interworx)