Fix language setting not being saved to database on admin settings page

- Added default_language field to general settings state in SettingsPage
- Replaced LanguageSelector component with simple select dropdown on settings page
- Fixed public settings endpoint to read general_default_language from database
- Language setting now properly saved when clicking Save Settings button
- Setting is correctly used by gallery login page and legal pages

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

backend/src/utils/filenameSanitizer.js

@@ -0,0 +1,57 @@
+/**
+ * Sanitize a string to be used as a filename component
+ * @param {string} str - The string to sanitize
+ * @param {number} maxLength - Maximum length of the sanitized string
+ * @returns {string} - Sanitized string
+ */
+function sanitizeFilename(str, maxLength = 50) {
+  if (!str) return 'unnamed';
+  
+  // Convert to string and trim
+  let sanitized = String(str).trim();
+  
+  // Replace spaces with underscores
+  sanitized = sanitized.replace(/\s+/g, '_');
+  
+  // Remove special characters except hyphens, underscores, and dots
+  sanitized = sanitized.replace(/[^a-zA-Z0-9_\-\.]/g, '');
+  
+  // Remove multiple consecutive underscores or hyphens
+  sanitized = sanitized.replace(/[_\-]{2,}/g, '_');
+  
+  // Remove leading/trailing underscores or hyphens
+  sanitized = sanitized.replace(/^[_\-]+|[_\-]+$/g, '');
+  
+  // Limit length
+  if (sanitized.length > maxLength) {
+    sanitized = sanitized.substring(0, maxLength);
+  }
+  
+  // If empty after sanitization, use default
+  if (!sanitized) {
+    sanitized = 'unnamed';
+  }
+  
+  return sanitized;
+}
+
+/**
+ * Generate a photo filename based on event name, category, and counter
+ * @param {string} eventName - The event name
+ * @param {string} categoryName - The category name
+ * @param {number} counter - The photo counter
+ * @param {string} extension - The file extension (including dot)
+ * @returns {string} - Generated filename
+ */
+function generatePhotoFilename(eventName, categoryName, counter, extension) {
+  const sanitizedEvent = sanitizeFilename(eventName, 30);
+  const sanitizedCategory = sanitizeFilename(categoryName || 'uncategorized', 20);
+  const paddedCounter = String(counter).padStart(4, '0');
+  
+  return `${sanitizedEvent}_${sanitizedCategory}_${paddedCounter}${extension}`;
+}
+
+module.exports = {
+  sanitizeFilename,
+  generatePhotoFilename
+};