feat: implement dedicated package shop page with legal confirmation

This commit:
- Creates MobilePackageShopPage.tsx for listing packages and handling checkout.
- Implements a confirmation screen with mandatory AGB and Withdrawal checkboxes.
- Registers the new route /mobile/billing/shop.
- Updates EventAnalyticsPage to link to the new shop page.
- Reverts previous inline upgrade logic in BillingPage.tsx.

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#packages'))}
+            onPress={() => navigate(adminPath('/mobile/billing/shop'))}
           />
         </MobileCard>
       </MobileShell>