Fix template rendering issue and improve export functionality

- Fix template rendering by storing rendered HTML in variable before writing
  This resolves subdirectories not appearing in navigation despite being
  correctly detected and included in template variables
- Add missing template variables (paths.work_dir) to gallery config
- Add CGI refresh handler for web-based gallery regeneration
- Improve PDF export functionality with better error handling
- Add ESC key shortcut documentation for exiting selection mode
- Enhanced export manager with proper dependency checking

Fixes issue where new subdirectories were detected but not displayed
in browser navigation due to incomplete template rendering.

assets/js/utils.js

@@ -105,8 +105,16 @@ export class Utils {
     refreshBtn.disabled = true;
     refreshBtn.textContent = '⏳';
     
+    // Use the CGI script path from config if available
+    let cgiPath = '/cgi-bin/refresh_gallery.py';
+    if (window.galleryConfig && window.galleryConfig.paths && window.galleryConfig.paths.cgi_script) {
+      cgiPath = window.galleryConfig.paths.cgi_script;
+      // Ensure it starts with a slash for fetch
+      if (!cgiPath.startsWith('/')) cgiPath = '/' + cgiPath;
+    }
+    
     try {
-      const response = await fetch('/cgi-bin/refresh_gallery.py', {
+      const response = await fetch(cgiPath, {
         method: 'POST',
         headers: {
           'Content-Type': 'application/json',