Security fix: Use JSON serialization for template variable in JavaScript

- Fixed XSS vulnerability in file detail template
- Use tojson filter to safely encode file.id into JavaScript
- CodeQL scan confirms no security issues

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

frontend/templates/file_detail.html

@@ -210,7 +210,7 @@
   <script>
     // JavaScript for handling retry functionality
     async function reprocessFile() {
-      const fileId = {{ file.id }};
+      const fileId = {{ file.id | tojson }};
       const button = document.getElementById('reprocess-btn');
       const statusDiv = document.getElementById('reprocess-status');