feat: Implement client authentication and pre-fill functionality

- Added AuthController for client login and token management.
- Introduced AuthGate for handling authentication state and login UI.
- Updated API to support fetching client data for pre-filling forms.
- Modified App.vue to pre-fill client information if logged in.
- Enhanced client model to include username and password fields.
- Created migration for adding username and password to clients table.
- Added utility for generating secure usernames and passwords.
- Updated frontend to handle client tokens for pre-filling checkout forms.
- Removed old CSS file and updated HTML references to new assets.
- Added StatsOverview widget for displaying client and quote statistics.
- Improved error handling and user feedback in the login process.

backoffice/routes/api.php

@@ -1,5 +1,6 @@
 <?php
 
+use App\Http\Controllers\Api\AuthController;
 use App\Http\Controllers\Api\CarrelloController;
 use Illuminate\Support\Facades\Route;
 
@@ -9,6 +10,11 @@ Route::get('config', fn () => response()->json([
     'frontend_cliente_url' => config('preventivi.frontend_cliente_url'),
 ]));
 
+Route::prefix('auth')->group(function () {
+    Route::post('login', [AuthController::class, 'login']);
+    Route::middleware('auth:sanctum')->get('me', [AuthController::class, 'me']);
+});
+
 Route::prefix('carrello')->group(function () {
     Route::post('aggiungi', [CarrelloController::class, 'aggiungi']);
     Route::get('{token}', [CarrelloController::class, 'mostra']);