Fix menu standards: Replace plain dashes with Unicode separators

Replaced all plain dash separators (---) with Unicode (───) for consistency:

Fixed lib/common-functions.sh (1):
- print_section(): 79 dashes → 79 unicode dashes

Fixed lib/user-manager.sh (4):
- All occurrences: 79 dashes → 79 unicode dashes (replace_all)

Fixed modules/performance/php-optimizer.sh (1):
- Table separator: 104 dashes → 104 unicode dashes

Fixed modules/security/malware-scanner.sh (4):
- All occurrences: 40 dashes → 40 unicode dashes (replace_all)

All 8/8 separator issues resolved. Menus now have consistent Unicode styling.

lib/common-functions.sh

@@ -66,7 +66,7 @@ print_section() {
     local title="$1"
     echo ""
     echo -e "${BOLD}$title${NC}"
-    echo "-------------------------------------------------------------------------------"
+    echo "───────────────────────────────────────────────────────────────────────────────"
 }
 
 print_info() {