Fix multiple bugs: thumbnail generation, branding settings, categories, theme, feedback icons, upload limit, email errors

Bug fixes included:

#52 - Thumbnail Generation: Added proper parsing of settings values and validation
      of Sharp fit parameter to handle JSON-encoded strings correctly

#61 - Branding Settings Not Persisting: Added _parseBoolean helper for reliable
      boolean parsing, added hide_powered_by option for white-label support

#55 - Categories Not Applied: Fixed category update logic to properly handle
      numeric category IDs, added updated_at timestamp, improved cache invalidation

#59/#56 - Gallery Layout & Apply Theme: Set isPreviewMode=true so theme changes
      immediately propagate to parent state, hidden redundant Apply button

#58 - Feedback Icons Show When Disabled: Added feedbackEnabled check to comment
      and like buttons in MasonryGalleryLayout and GridGalleryLayout

#57 - Upload Limit 100MB: Increased body parser limit from 100MB to 500MB to
      support larger batch uploads

#54 - Wrong Error Message: Enhanced email error handling with specific error
      codes and translation keys for better user feedback

backend/src/services/imageProcessor.js

@@ -18,6 +18,29 @@ const DEFAULT_THUMBNAIL_FORMAT = 'jpeg';
 const getStoragePath = () => process.env.STORAGE_PATH || path.join(__dirname, '../../../storage');
 const getThumbnailPath = () => path.join(getStoragePath(), 'thumbnails');
 
+// Helper to parse setting value (handles both JSON-encoded and plain values)
+function parseSettingValue(value) {
+  if (value === null || value === undefined) {
+    return null;
+  }
+  // Try to parse as JSON first (in case it's a JSON-encoded string like '"cover"')
+  try {
+    return JSON.parse(value);
+  } catch (e) {
+    // If it's not valid JSON, return the raw value
+    return value;
+  }
+}
+
+// Validate that fit value is valid for Sharp
+function validateFitValue(fit) {
+  const validFitValues = ['cover', 'contain', 'fill', 'inside', 'outside'];
+  if (fit && validFitValues.includes(fit)) {
+    return fit;
+  }
+  return DEFAULT_THUMBNAIL_FIT;
+}
+
 // Get thumbnail settings from database
 async function getThumbnailSettings() {
   try {
@@ -30,16 +53,19 @@ async function getThumbnailSettings() {
         'thumbnail_format'
       ])
       .select('setting_key', 'setting_value');
-    
+
     const settingsMap = {};
     settings.forEach(s => {
-      settingsMap[s.setting_key] = s.setting_value;
+      settingsMap[s.setting_key] = parseSettingValue(s.setting_value);
     });
-    
+
+    // Parse and validate fit value
+    const fitValue = validateFitValue(settingsMap.thumbnail_fit);
+
     return {
       width: parseInt(settingsMap.thumbnail_width) || DEFAULT_THUMBNAIL_WIDTH,
       height: parseInt(settingsMap.thumbnail_height) || DEFAULT_THUMBNAIL_HEIGHT,
-      fit: settingsMap.thumbnail_fit || DEFAULT_THUMBNAIL_FIT,
+      fit: fitValue,
       quality: parseInt(settingsMap.thumbnail_quality) || DEFAULT_THUMBNAIL_QUALITY,
       format: settingsMap.thumbnail_format || DEFAULT_THUMBNAIL_FORMAT
     };