Add PayPal, Stripe, CSV-Export; fix .env.production issue

- PayPal: Checkout-Integration via srmklive/paypal, Weiterleitung zu PayPal,
  Bestellung wird nach Capture automatisch auf payment_received gesetzt
- Stripe: Payment Elements im Checkout, Intent-API, Zahlung direkt bestätigt
- CSV-Export: Admin → Bestellungen → CSV exportieren (UTF-8 BOM für Excel)
- PayPal/Stripe nur sichtbar wenn Keys in .env gesetzt
- .env.example um PAYPAL_* und STRIPE_* Keys erweitert

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

config/paypal.php

@@ -0,0 +1,31 @@
+<?php
+
+/**
+ * PayPal Setting & API Credentials
+ * Created by Raza Mehdi <srmk@outlook.com>.
+ */
+
+return [
+    'mode' => env('PAYPAL_MODE', 'sandbox'), // Can only be 'sandbox' Or 'live'. If empty or invalid, 'live' will be used.
+    'sandbox' => [
+        'client_id' => env('PAYPAL_SANDBOX_CLIENT_ID', ''),
+        'client_secret' => env('PAYPAL_SANDBOX_CLIENT_SECRET', ''),
+        'app_id' => 'APP-80W284485P519543T', // Sandbox app_id is always this fixed value.
+    ],
+    'live' => [
+        'client_id' => env('PAYPAL_LIVE_CLIENT_ID', ''),
+        'client_secret' => env('PAYPAL_LIVE_CLIENT_SECRET', ''),
+        // Live app_id: log in to developer.paypal.com → My Apps & Credentials →
+        // select your app → the App ID shown at the top (starts with "APP-").
+        'app_id' => env('PAYPAL_LIVE_APP_ID', ''),
+    ],
+
+    'payment_action' => env('PAYPAL_PAYMENT_ACTION', 'Sale'), // Can only be 'Sale', 'Authorization' or 'Order'
+    'currency' => env('PAYPAL_CURRENCY', 'USD'),
+    'notify_url' => env('PAYPAL_NOTIFY_URL', ''), // Change this accordingly for your application.
+    'locale' => env('PAYPAL_LOCALE', 'en_US'), // force gateway language  i.e. it_IT, es_ES, en_US ... (for express checkout only)
+    'validate_ssl' => env('PAYPAL_VALIDATE_SSL', true), // Validate SSL when creating api client.
+    'timeout' => env('PAYPAL_TIMEOUT', 30), // Total request timeout in seconds.
+    'connect_timeout' => env('PAYPAL_CONNECT_TIMEOUT', 10), // Connection timeout in seconds.
+    'max_retries' => env('PAYPAL_MAX_RETRIES', 2), // Retries on 5xx / connection errors (0 to disable). Uses exponential backoff.
+];

config/services.php

@@ -28,6 +28,11 @@ return [
         'region' => env('AWS_DEFAULT_REGION', 'us-east-1'),
     ],
 
+    'stripe' => [
+        'key'    => env('STRIPE_KEY'),
+        'secret' => env('STRIPE_SECRET'),
+    ],
+
     'slack' => [
         'notifications' => [
             'bot_user_oauth_token' => env('SLACK_BOT_USER_OAUTH_TOKEN'),