CRITICAL: Guarantee menu loop NEVER exits to command line

Added explicit safeguards to ensure the menu loop ALWAYS returns to menu:

1. Check for empty menu_choice (handles EOF/Ctrl-D)
   - If empty, show error and continue (don't break loop)

2. Added infinite loop guarantee comment
   - The 'while true' should ONLY exit via explicit return 0 on option [0]

3. Added safety fallback at end of main()
   - If loop somehow breaks, return 0 gracefully

REQUIREMENT: Pressing Enter at ANY prompt should return to menu,
EXCEPT when user explicitly selects [0] to exit.

This prevents the script from unexpectedly exiting to command line
and ensures users always get back to the main menu to try again.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

modules/backup/mysql-restore-to-sql.sh

@@ -2950,9 +2950,17 @@ main() {
     local menu_choice=""
 
     while true; do
+        # Infinite loop - only exits with explicit "return 0" on option [0]
         show_step_menu
         read -r menu_choice
 
+        # Ensure menu_choice is not empty (handle EOF/Ctrl-D)
+        if [ -z "$menu_choice" ]; then
+            print_error "Invalid option (empty input). Returning to menu."
+            press_enter
+            continue
+        fi
+
         case $menu_choice in
             1)
                 # Step 1: Detect live data directory
@@ -3138,6 +3146,10 @@ main() {
                 ;;
         esac
     done
+
+    # SAFETY: This line should never be reached (loop is infinite)
+    # But if it somehow is, return 0 to exit gracefully
+    return 0
 }
 
 # Run main function