Refactor API structure and integrate new modular API client

- Replaced legacy apiService with a new modular api client structure.
- Updated AuthContext, OAuthButtons, and AuthCallbackPage to use the new api client.
- Created separate services for auth, sounds, playlists, and users.
- Implemented centralized API configuration and error handling.
- Added support for OAuth providers and token exchange.
- Introduced a Toaster component for notifications in App.
- Updated API endpoints and request handling for better maintainability.

src/App.tsx

@@ -5,6 +5,7 @@ import { LoginPage } from './pages/LoginPage'
 import { RegisterPage } from './pages/RegisterPage'
 import { AuthCallbackPage } from './pages/AuthCallbackPage'
 import { DashboardPage } from './pages/DashboardPage'
+import { Toaster } from './components/ui/sonner'
 
 function ProtectedRoute({ children }: { children: React.ReactNode }) {
   const { user, loading } = useAuth()
@@ -20,7 +21,6 @@ function ProtectedRoute({ children }: { children: React.ReactNode }) {
   return <>{children}</>
 }
 
-
 function AppRoutes() {
   const { user } = useAuth()
   
@@ -43,6 +43,7 @@ function App() {
     <ThemeProvider defaultTheme="dark" storageKey="vite-ui-theme">
       <AuthProvider>
         <AppRoutes />
+        <Toaster />
       </AuthProvider>
     </ThemeProvider>
   )