feat: Implement dark mode support across the application

- Added ThemeContext to manage theme state and toggle functionality.
- Updated components to support dark mode styles, including header, dashboard, and home page.
- Enhanced CSS for smooth transitions between light and dark themes.
- Modified authentication context to handle async login operations.
- Improved user experience by preserving theme preference in local storage.
- Refactored login and register pages to handle OAuth tokens and errors more gracefully.

ospabhost/frontend/src/pages/register.tsx

@@ -99,20 +99,24 @@ const RegisterPage = () => {
 
   // Handle OAuth token from URL
   useEffect(() => {
-    const params = new URLSearchParams(location.search);
-    const token = params.get('token');
-    const authError = params.get('error');
+    const handleOAuthLogin = async () => {
+      const params = new URLSearchParams(location.search);
+      const token = params.get('token');
+      const authError = params.get('error');
 
-    if (token) {
-      login(token);
-      navigate(localePath('/dashboard'), { replace: true });
-    }
+      if (token) {
+        await login(token);
+        navigate(localePath('/dashboard'), { replace: true });
+      }
 
-    if (authError) {
-      setError(locale === 'en' 
-        ? 'Social login error. Please try again.' 
-        : 'Ошибка авторизации через социальную сеть. Попробуйте снова.');
-    }
+      if (authError) {
+        setError(locale === 'en' 
+          ? 'Social login error. Please try again.' 
+          : 'Ошибка авторизации через социальную сеть. Попробуйте снова.');
+      }
+    };
+
+    handleOAuthLogin();
   }, [location, login, navigate, localePath, locale]);
 
   const handleRegister = async (e: React.FormEvent) => {
@@ -288,7 +292,7 @@ const RegisterPage = () => {
             </div>
           </div>
 
-          <div className="mt-6 grid grid-cols-4 gap-3">
+          <div className="mt-6 grid grid-cols-3 gap-3">
             <button
               type="button"
               onClick={() => handleOAuthLogin('google')}
@@ -315,15 +319,6 @@ const RegisterPage = () => {
             >
               <img src="/yandex.png" alt="" className="h-6 w-6" />
             </button>
-
-            <button
-              type="button"
-              onClick={() => handleOAuthLogin('vkontakte')}
-              className="flex items-center justify-center h-12 rounded-full border border-gray-300 bg-white shadow-sm hover:bg-gray-50 transition"
-              aria-label={locale === 'en' ? 'Sign up with VK' : 'Регистрация через VK'}
-            >
-              <img src="/vk.svg" alt="VK" className="h-6 w-6" />
-            </button>
           </div>
         </div>