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 <noreply@anthropic.com>

frontend/src/contexts/ThemeContext.tsx

@@ -1,4 +1,4 @@
-import React, { createContext, useContext, useState, useEffect } from 'react';
+import React, { createContext, useContext, useState, useEffect, useCallback, useMemo } from 'react';
 import type { ReactNode } from 'react';
 
 export interface ThemeConfig {
@@ -107,7 +107,7 @@ export const ThemeProvider: React.FC<ThemeProviderProps> = ({
   const [theme, setTheme] = useState<ThemeConfig>(initialTheme);
   const [themeName, setThemeName] = useState(initialThemeName);
 
-  const applyTheme = (themeConfig: ThemeConfig) => {
+  const applyTheme = useCallback((themeConfig: ThemeConfig) => {
     const root = document.documentElement;
     
     // Apply CSS variables
@@ -154,56 +154,76 @@ export const ThemeProvider: React.FC<ThemeProviderProps> = ({
       }
       styleElement.textContent = themeConfig.customCss;
     }
-  };
+  }, []);
 
-  const setThemeByName = (name: string) => {
+  const setThemeConfig = useCallback((newTheme: ThemeConfig) => {
+    setTheme(newTheme);
+    applyTheme(newTheme);
+  }, [applyTheme]);
+
+  const setThemeByName = useCallback((name: string) => {
     const presetTheme = PRESET_THEMES[name];
     if (presetTheme) {
       setThemeName(name);
       setTheme(presetTheme.config);
       applyTheme(presetTheme.config);
     }
-  };
+  }, [applyTheme]);
 
-  const resetTheme = () => {
+  const resetTheme = useCallback(() => {
     setThemeByName('default');
-  };
+  }, [setThemeByName]);
 
+  // Apply theme when it changes, but skip if it's the same
   useEffect(() => {
-    applyTheme(theme);
-  }, [theme]);
+    const root = document.documentElement;
+    const currentPrimary = root.style.getPropertyValue('--color-primary');
+    
+    // Only apply if the theme has actually changed
+    if (currentPrimary !== theme.primaryColor) {
+      applyTheme(theme);
+    }
+  }, [theme, applyTheme]);
 
-  // Load theme from localStorage on mount
+  // Load theme from localStorage on mount (skip if in gallery view)
   useEffect(() => {
-    const savedTheme = localStorage.getItem('gallery-theme');
-    if (savedTheme) {
-      try {
-        const parsed = JSON.parse(savedTheme);
-        setTheme(parsed.config);
-        setThemeName(parsed.name);
-      } catch (e) {
-        console.error('Failed to load saved theme:', e);
+    // Check if we're in a gallery view by looking at the URL
+    const isGalleryView = window.location.pathname.includes('/gallery/');
+    if (!isGalleryView) {
+      const savedTheme = localStorage.getItem('gallery-theme');
+      if (savedTheme) {
+        try {
+          const parsed = JSON.parse(savedTheme);
+          setTheme(parsed.config);
+          setThemeName(parsed.name);
+        } catch (e) {
+          console.error('Failed to load saved theme:', e);
+        }
       }
     }
   }, []);
 
   // Save theme to localStorage when it changes
   useEffect(() => {
-    localStorage.setItem('gallery-theme', JSON.stringify({ name: themeName, config: theme }));
+    // Only save if theme has actually changed
+    const currentSaved = localStorage.getItem('gallery-theme');
+    const newValue = JSON.stringify({ name: themeName, config: theme });
+    if (currentSaved !== newValue) {
+      localStorage.setItem('gallery-theme', newValue);
+    }
   }, [theme, themeName]);
 
+  const contextValue = useMemo(() => ({
+    theme,
+    themeName,
+    setTheme: setThemeConfig,
+    setThemeByName,
+    applyTheme,
+    resetTheme
+  }), [theme, themeName, setThemeConfig, setThemeByName, applyTheme, resetTheme]);
+
   return (
-    <ThemeContext.Provider value={{ 
-      theme, 
-      themeName, 
-      setTheme: (newTheme) => {
-        setTheme(newTheme);
-        applyTheme(newTheme);
-      },
-      setThemeByName,
-      applyTheme,
-      resetTheme 
-    }}>
+    <ThemeContext.Provider value={contextValue}>
       {children}
     </ThemeContext.Provider>
   );