fix: resolve subscription ID lookup and checkout URL issues

- Fix getBaseUrl() ReferenceError by changing to resolveBaseUrl(req) for free-to-paid upgrades
- Add subscription lookup by customer email when dodoSubscriptionId is missing
- Log critical issues when paid users have no subscription ID in database or Dodo
- Return clear error message to contact support when subscription cannot be found
- Prevent silent failures in plan changes from settings page

chat/public/apps.html

@@ -2247,7 +2247,7 @@
       }
 
       const tourSteps = [
-        { target: null, color: '#008060' },
+        { target: '#apps-content', color: '#008060' },
         { target: '#create-new-app', color: '#5A31F4' },
         { target: '#upload-app-btn', color: '#F59E0B' },
         { target: '#browse-templates-btn', color: '#10B981' },