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>

routes/web.php

@@ -25,6 +25,15 @@ Route::post('/kasse/adresse', [Shop\CheckoutController::class, 'storeAddress'])-
 Route::get('/kasse/zahlung', [Shop\CheckoutController::class, 'payment'])->name('checkout.payment');
 Route::match(['GET','POST'], '/kasse/bestaetigen', [Shop\CheckoutController::class, 'confirm'])->name('checkout.confirm');
 Route::get('/kasse/danke/{order}', [Shop\CheckoutController::class, 'thankyou'])->name('checkout.thankyou');
+// PayPal
+Route::get('/kasse/paypal/weiterleitung', [Shop\PayPalController::class, 'redirect'])->name('paypal.redirect');
+Route::get('/kasse/paypal/erfolg', [Shop\PayPalController::class, 'success'])->name('paypal.success');
+Route::get('/kasse/paypal/abbruch', [Shop\PayPalController::class, 'cancel'])->name('paypal.cancel');
+
+// Stripe
+Route::post('/kasse/stripe/intent', [Shop\StripeController::class, 'createIntent'])->name('stripe.intent');
+Route::get('/kasse/stripe/erfolg', [Shop\StripeController::class, 'success'])->name('stripe.success');
+
 Route::post('/kasse/gutschein', [Shop\CheckoutController::class, 'applyCoupon'])->name('checkout.coupon.apply');
 Route::post('/kasse/gutschein/entfernen', [Shop\CheckoutController::class, 'removeCoupon'])->name('checkout.coupon.remove');
 Route::get('/kasse/versandkosten', [Shop\CheckoutController::class, 'shippingCost'])->name('checkout.shipping.cost');
@@ -86,6 +95,7 @@ Route::middleware(['auth', 'admin'])->prefix('admin')->name('admin.')->group(fun
 
     // Bestellungen
     Route::get('orders', [Admin\OrderController::class, 'index'])->name('orders.index');
+    Route::get('orders/export/csv', [Admin\OrderController::class, 'exportCsv'])->name('orders.export');
     Route::get('orders/{order}', [Admin\OrderController::class, 'show'])->name('orders.show');
     Route::put('orders/{order}/status', [Admin\OrderController::class, 'updateStatus'])->name('orders.status');
     Route::post('orders/{order}/invoice', [Admin\OrderController::class, 'sendInvoice'])->name('orders.invoice');