Enhance email templates with clickable links, branding, and improved styling

- Add clickable gallery links in all email templates
- Include application logo in email header and footer (custom or PicPeak default)
- Redesign emails with professional styling matching gallery login page
  - Gray background with white content box
  - PicPeak green header with centered logo
  - Clean typography and proper spacing
  - Responsive design for mobile devices
  - Styled call-to-action buttons
  - Footer with branding and copyright
- Update email processor to fetch branding settings dynamically
- Use proper API URLs for logo images in emails

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

Co-Authored-By: Claude <noreply@anthropic.com>

backend/src/routes/adminSettings.js

@@ -133,7 +133,10 @@ router.put('/branding', adminAuth, async (req, res) => {
       watermark_enabled,
       watermark_position,
       watermark_opacity,
-      watermark_size
+      watermark_size,
+      favicon_url,
+      logo_url,
+      watermark_logo_url
     } = req.body;
 
     const brandingSettings = {
@@ -144,9 +147,72 @@ router.put('/branding', adminAuth, async (req, res) => {
       watermark_enabled,
       watermark_position,
       watermark_opacity,
-      watermark_size
+      watermark_size,
+      favicon_url,
+      logo_url,
+      watermark_logo_url
     };
 
+    // Handle favicon deletion if empty string or null is provided
+    if (favicon_url === '' || favicon_url === null || favicon_url === undefined) {
+      // Get current favicon path to delete file
+      const currentFaviconSetting = await db('app_settings')
+        .where('setting_key', 'branding_favicon_url')
+        .first();
+      
+      if (currentFaviconSetting && currentFaviconSetting.setting_value) {
+        let currentFaviconUrl;
+        try {
+          // Try to parse as JSON first
+          currentFaviconUrl = JSON.parse(currentFaviconSetting.setting_value);
+        } catch (e) {
+          // If it's not valid JSON, use the raw value
+          currentFaviconUrl = currentFaviconSetting.setting_value;
+        }
+        
+        if (currentFaviconUrl && typeof currentFaviconUrl === 'string' && currentFaviconUrl.startsWith('/uploads/favicons/')) {
+          // Delete the file from filesystem
+          const faviconPath = path.join(__dirname, '..', '..', 'storage', currentFaviconUrl.replace('/uploads/', ''));
+          try {
+            await fs.unlink(faviconPath);
+            console.log('Deleted favicon file:', faviconPath);
+          } catch (err) {
+            console.error('Error deleting favicon file:', err);
+          }
+        }
+      }
+    }
+
+    // Handle logo deletion if empty string or null is provided
+    if (logo_url === '' || logo_url === null || logo_url === undefined) {
+      // Get current logo path to delete file
+      const currentLogoSetting = await db('app_settings')
+        .where('setting_key', 'branding_logo_url')
+        .first();
+      
+      if (currentLogoSetting && currentLogoSetting.setting_value) {
+        let currentLogoUrl;
+        try {
+          // Try to parse as JSON first
+          currentLogoUrl = JSON.parse(currentLogoSetting.setting_value);
+        } catch (e) {
+          // If it's not valid JSON, use the raw value
+          currentLogoUrl = currentLogoSetting.setting_value;
+        }
+        
+        if (currentLogoUrl && typeof currentLogoUrl === 'string' && currentLogoUrl.startsWith('/uploads/logos/')) {
+          // Delete the file from filesystem
+          const logoPath = path.join(__dirname, '..', '..', 'storage', currentLogoUrl.replace('/uploads/', ''));
+          try {
+            await fs.unlink(logoPath);
+            console.log('Deleted logo file:', logoPath);
+          } catch (err) {
+            console.error('Error deleting logo file:', err);
+          }
+        }
+      }
+    }
+
     // Update or insert each setting
     for (const [key, value] of Object.entries(brandingSettings)) {
       await db('app_settings')