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/user-manager.sh

@@ -41,8 +41,9 @@ list_all_users() {
 
 # cPanel user listing
 list_cpanel_users() {
-    if [ -d "/var/cpanel/users" ]; then
-        ls /var/cpanel/users/ 2>/dev/null || true
+    local cpanel_users_dir="${SYS_CPANEL_USERS_DIR:-/var/cpanel/users}"
+    if [ -d "$cpanel_users_dir" ]; then
+        ls "$cpanel_users_dir" 2>/dev/null || true
     else
         # Fallback: parse /etc/trueuserdomains
         awk -F: '{print $2}' /etc/trueuserdomains 2>/dev/null | sort -u || true
@@ -108,7 +109,7 @@ get_user_info() {
 # cPanel user info
 get_cpanel_user_info() {
     local username="$1"
-    local user_file="/var/cpanel/users/${username}"
+    local user_file="${SYS_CPANEL_USERS_DIR:-/var/cpanel/users}/${username}"
 
     if [ ! -f "$user_file" ]; then
         echo "USER_EXISTS=no"