feat: implement gallery logo customization (Issue #17)

Added comprehensive logo customization features for gallery views:
- Logo size options (small, medium, large, xlarge, custom)
- Logo position control (left, center, right)
- Display mode settings (logo only, text only, logo and text)
- Visibility controls for header and hero sections
- Custom height configuration for fine-tuning

Changes:
- Added database migration for 6 new logo customization settings
- Extended backend APIs to handle logo customization fields
- Updated GalleryLayout.tsx with dynamic logo rendering logic
- Added logo upload functionality to BrandingPage.tsx
- Extended settings service with logo customization types

This addresses the issue where the gallery logo was "very large and centered"
by providing full control over logo appearance and positioning.

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

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

backend/src/routes/adminSettings.js

@@ -170,7 +170,13 @@ router.put('/branding', adminAuth, async (req, res) => {
       watermark_size,
       favicon_url,
       logo_url,
-      watermark_logo_url
+      watermark_logo_url,
+      logo_size,
+      logo_max_height,
+      logo_position,
+      logo_display_header,
+      logo_display_hero,
+      logo_display_mode
     } = req.body;
 
     const brandingSettings = {
@@ -184,7 +190,13 @@ router.put('/branding', adminAuth, async (req, res) => {
       watermark_size,
       favicon_url,
       logo_url,
-      watermark_logo_url
+      watermark_logo_url,
+      logo_size,
+      logo_max_height,
+      logo_position,
+      logo_display_header,
+      logo_display_hero,
+      logo_display_mode
     };
 
     // Handle favicon deletion if empty string or null is provided

backend/src/routes/publicSettings.js

@@ -42,6 +42,12 @@ router.get('/', async (req, res) => {
       branding_watermark_size: settingsObject.branding_watermark_size || 15,
       branding_favicon_url: settingsObject.branding_favicon_url || '',
       branding_logo_url: settingsObject.branding_logo_url || '',
+      branding_logo_size: settingsObject.branding_logo_size || 'medium',
+      branding_logo_max_height: settingsObject.branding_logo_max_height || 48,
+      branding_logo_position: settingsObject.branding_logo_position || 'left',
+      branding_logo_display_header: settingsObject.branding_logo_display_header !== false,
+      branding_logo_display_hero: settingsObject.branding_logo_display_hero !== false,
+      branding_logo_display_mode: settingsObject.branding_logo_display_mode || 'logo_and_text',
       theme_config: settingsObject.theme_config || null,
       default_language: settingsObject.general_default_language || 'en',
       enable_analytics: settingsObject.general_enable_analytics !== false,