Wallet-Topup ueber Stripe (Credit-Pakete mit Bonus-Staffel)

End-to-end-Aufladung der Credit-Wallet, spiegelt den Einzel-PM-Fluss:

- Paket-Staffel mit Bonus in config/credits.php (10->10, 25->27, 50->55,
  100->115 Credits; price_cents netto, Stripe Tax ergaenzt USt.)
- credit_topups (Pending->Paid) + CreditTopupService: startTopup legt den
  Pending-Kauf an, fulfill() schreibt die Wallet idempotent gut (credited_at)
- StripeCheckoutService::forCreditTopup via checkoutCharge + credit_topup_id
  Metadata; ProcessStripeWebhook schreibt bei checkout.session.completed gut
- Checkout-Route /admin/me/checkout/credits/{pack} mit Rechnungsadress-Gate

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/Services/Billing/StripeCheckoutService.php

@@ -2,6 +2,7 @@
 
 namespace App\Services\Billing;
 
+use App\Models\CreditTopup;
 use App\Models\Plan;
 use App\Models\SinglePurchase;
 use App\Models\User;
@@ -117,4 +118,24 @@ class StripeCheckoutService
             'metadata' => ['single_purchase_id' => (string) $purchase->id],
         ]);
     }
+
+    /**
+     * Stripe-Checkout für eine Wallet-Aufladung. Ad-hoc-Charge über den
+     * Netto-Paketpreis (Stripe Tax ergänzt die USt.); die `credit_topup_id`
+     * in den Metadaten schließt den Kreis im Webhook (Wallet-Gutschrift).
+     */
+    public function forCreditTopup(User $user, CreditTopup $topup): Checkout
+    {
+        $this->syncTaxIdFromBillingAddress($user);
+
+        return $user->checkoutCharge(
+            $topup->price_cents,
+            "Credit-Guthaben ({$topup->credits} Credits)",
+            1,
+            [
+                ...$this->sessionOptions(),
+                'metadata' => ['credit_topup_id' => (string) $topup->id],
+            ],
+        );
+    }
 }