feat: implement upgrade to premium flow

This commit adds the ability for tenants to upgrade their package directly from the mobile billing page. It includes:
- New API function createTenantPaddleCheckout in api.ts
- Upgrade handler and UI in BillingPage.tsx
- Updated navigation in EventAnalyticsPage.tsx to link to the packages section of the billing page

resources/js/admin/mobile/BillingPage.tsx

@@ -14,6 +14,7 @@ import {
   getTenantPaddleTransactions,
   TenantPackageSummary,
   PaddleTransactionSummary,
+  createTenantPaddleCheckout,
 } from '../api';
 import { TenantAddonHistoryEntry, getTenantAddonHistory } from '../api';
 import { getApiErrorMessage } from '../lib/apiError';
@@ -40,6 +41,7 @@ export default function MobileBillingPage() {
   const [loading, setLoading] = React.useState(true);
   const [error, setError] = React.useState<string | null>(null);
   const [portalBusy, setPortalBusy] = React.useState(false);
+  const [upgradeBusy, setUpgradeBusy] = React.useState<number | null>(null);
   const packagesRef = React.useRef<HTMLDivElement | null>(null);
   const invoicesRef = React.useRef<HTMLDivElement | null>(null);
   const supportEmail = 'support@fotospiel.de';
@@ -95,6 +97,26 @@ export default function MobileBillingPage() {
     }
   }, [portalBusy, t]);
 
+  const handleUpgrade = React.useCallback(async (pkg: TenantPackageSummary) => {
+    if (upgradeBusy) return;
+    setUpgradeBusy(pkg.package_id);
+    
+    try {
+        const { checkout_url } = await createTenantPaddleCheckout(pkg.package_id, {
+            success_url: window.location.href,
+            return_url: window.location.href,
+        });
+        
+        if (typeof window !== 'undefined') {
+            window.location.href = checkout_url;
+        }
+    } catch (err) {
+        const message = getApiErrorMessage(err, t('billing.errors.upgrade', 'Konnte Checkout nicht starten.'));
+        toast.error(message);
+        setUpgradeBusy(null);
+    }
+  }, [upgradeBusy, t]);
+
   React.useEffect(() => {
     void load();
   }, [load]);
@@ -161,7 +183,12 @@ export default function MobileBillingPage() {
             {packages
               .filter((pkg) => !activePackage || pkg.id !== activePackage.id)
               .map((pkg) => (
-                <PackageCard key={pkg.id} pkg={pkg} />
+                <PackageCard 
+                    key={pkg.id} 
+                    pkg={pkg} 
+                    onUpgrade={() => handleUpgrade(pkg)}
+                    upgradeBusy={upgradeBusy === pkg.package_id}
+                />
               ))}
           </YStack>
         )}
@@ -265,12 +292,16 @@ function PackageCard({
   isActive = false,
   onOpenPortal,
   portalBusy,
+  onUpgrade,
+  upgradeBusy,
 }: {
   pkg: TenantPackageSummary;
   label?: string;
   isActive?: boolean;
   onOpenPortal?: () => void;
   portalBusy?: boolean;
+  onUpgrade?: () => void;
+  upgradeBusy?: boolean;
 }) {
   const { t } = useTranslation('management');
   const { border, primary, accentSoft, textStrong, muted } = useAdminTheme();
@@ -383,6 +414,14 @@ function PackageCard({
           tone={isDanger ? 'danger' : 'primary'}
         />
       ) : null}
+      {!isActive && onUpgrade ? (
+        <CTAButton
+            label={upgradeBusy ? t('billing.actions.upgradeBusy', 'Einen Moment...') : t('billing.actions.upgrade', 'Buy / Upgrade')}
+            onPress={onUpgrade}
+            disabled={upgradeBusy}
+            tone="primary"
+        />
+      ) : null}
     </MobileCard>
   );
 }

resources/js/admin/mobile/EventAnalyticsPage.tsx

@@ -66,7 +66,7 @@ export default function MobileEventAnalyticsPage() {
           </YStack>
           <CTAButton
             label={t('analytics.upgradeAction', 'Upgrade to Premium')}
-            onPress={() => navigate(adminPath('/mobile/billing'))}
+            onPress={() => navigate(adminPath('/mobile/billing#packages'))}
           />
         </MobileCard>
       </MobileShell>