Add file details to copyright header check failure output

When copyright header check fails, now outputs the actual first 5 lines
of each failing file to help diagnose the issue.

.gitea/workflows/licence-check.yml

@@ -81,6 +81,9 @@ jobs:
             if ! head -n 5 "$file" | grep -qiE "Copyright.*[0-9]{4}.*MIT"; then
               echo "❌ Missing MIT-compliant copyright header in: $file"
               echo "   Required format: // Copyright (c) YYYY Name. MIT License."
+              echo "   Actual first 5 lines:"
+              head -n 5 "$file" | sed 's/^/     /'
+              echo ""
               MISSING_HEADER=$((MISSING_HEADER + 1))
             fi
           done <<< "$SOURCE_FILES"