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]>

frontend/src/services/settings.service.ts

@@ -6,7 +6,12 @@ export interface BrandingSettings {
   support_email: string;
   footer_text: string;
   watermark_enabled: boolean;
+  watermark_position?: 'bottom-right' | 'bottom-left' | 'top-right' | 'top-left' | 'center';
+  watermark_opacity?: number;
+  watermark_size?: number;
+  watermark_logo_url?: string;
   logo_url?: string;
+  favicon_url?: string;
 }
 
 export interface ThemeSettings {
@@ -50,11 +55,11 @@ export const settingsService = {
   },
 
   // Upload logo
-  async uploadLogo(file: File): Promise<{ logo_url: string }> {
+  async uploadLogo(file: File): Promise<string> {
     const formData = new FormData();
     formData.append('logo', file);
     
-    const response = await api.post<{ message: string; logo_url: string }>(
+    const response = await api.post<{ logoUrl: string }>(
       '/api/admin/settings/logo',
       formData,
       {
@@ -64,7 +69,43 @@ export const settingsService = {
       }
     );
     
-    return { logo_url: response.data.logo_url };
+    return response.data.logoUrl;
+  },
+
+  // Upload favicon
+  async uploadFavicon(file: File): Promise<string> {
+    const formData = new FormData();
+    formData.append('favicon', file);
+    
+    const response = await api.post<{ faviconUrl: string }>(
+      '/api/admin/settings/favicon',
+      formData,
+      {
+        headers: {
+          'Content-Type': 'multipart/form-data'
+        }
+      }
+    );
+    
+    return response.data.faviconUrl;
+  },
+
+  // Upload watermark logo
+  async uploadWatermarkLogo(file: File): Promise<string> {
+    const formData = new FormData();
+    formData.append('watermarkLogo', file);
+    
+    const response = await api.post<{ watermarkLogoUrl: string }>(
+      '/api/admin/settings/branding/watermark-logo',
+      formData,
+      {
+        headers: {
+          'Content-Type': 'multipart/form-data'
+        }
+      }
+    );
+    
+    return response.data.watermarkLogoUrl;
   },
 
   // Update theme settings
@@ -91,7 +132,12 @@ export const settingsService = {
       support_email: rawSettings.branding_support_email || '',
       footer_text: rawSettings.branding_footer_text || '',
       watermark_enabled: rawSettings.branding_watermark_enabled || false,
-      logo_url: rawSettings.branding_logo_url || undefined
+      watermark_position: rawSettings.branding_watermark_position || 'bottom-right',
+      watermark_opacity: rawSettings.branding_watermark_opacity || 50,
+      watermark_size: rawSettings.branding_watermark_size || 15,
+      watermark_logo_url: rawSettings.branding_watermark_logo_url || undefined,
+      logo_url: rawSettings.branding_logo_url || undefined,
+      favicon_url: rawSettings.branding_favicon_url || undefined
     };
   },