Fix duration validation in convert_audio.sh

- Replace printf with awk for better cross-platform compatibility
- Fixes 'érvénytelen szám' (invalid number) error on some systems
- Add null check for duration value

scripts/convert_audio.sh

@@ -90,8 +90,9 @@ validate_duration() {
     
     duration=$(ffprobe -v quiet -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 "$file" 2>/dev/null)
     
-    if [ $? -eq 0 ]; then
-        duration_int=$(printf "%.0f" "$duration")
+    if [ $? -eq 0 ] && [ -n "$duration" ]; then
+        # Convert to integer using awk for better compatibility
+        duration_int=$(echo "$duration" | awk '{print int($1)}')
         if [ "$duration_int" -ge "$expected_min" ] && [ "$duration_int" -le "$expected_max" ]; then
             echo -e "${GREEN}✓ Duration validation passed: ${duration}s${NC}"
         else