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)

lib/php-detector.sh

@@ -66,7 +66,7 @@ detect_php_version_for_domain() {
     case "$SYS_CONTROL_PANEL" in
         cpanel)
             # Check userdata for PHP version
-            local userdata_file="/var/cpanel/userdata/$username/$domain"
+            local userdata_file="${SYS_CPANEL_USERDATA_DIR:-/var/cpanel/userdata}/$username/$domain"
             if [ -f "$userdata_file" ]; then
                 local php_ver=$(grep "phpversion:" "$userdata_file" | awk '{print $2}' | tr -d "'\"")
                 echo "$php_ver"