Add lead tracking parameter to demo form submission (#1478)

* Add lead tracking parameter to demo form submission

- Replace thank you modal with redirect to /pricing?lead=1 after successful form submission
- Enables Google Analytics to track successful lead submissions via URL parameter
- Maintains all existing form validation and PostHog event tracking

Co-Authored-By: [email protected] <[email protected]>

* Show thank you modal AND redirect to pricing page with lead parameter

- Yield both ThankYouDialogState.push(True) and rx.redirect('/pricing?lead=1')
- Provides immediate user feedback via modal while enabling GA tracking via URL parameter
- Maintains all existing form validation and PostHog event tracking

Co-Authored-By: [email protected] <[email protected]>

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: [email protected] <[email protected]>

Author: devin-ai-integration[bot]

pcweb/pages/pricing/header.py

@@ -184,8 +184,8 @@ def submit(self, form_data: dict[str, Any]):
             # Send to PostHog for all submissions
             yield QuoteFormState.send_demo_event(form_data)
 
-            # Show thank you modal for all submissions
             yield ThankYouDialogState.push(True)
+            yield rx.redirect("/pricing?lead=1")
             return