feat: handling subscription tier button link parameter (#7553)

## Summary

Discussion here:
https://comfy-organization.slack.com/archives/C0A0XANFJRE/p1764899027465379

Implement: Subscription tier query parameter for direct checkout flow

Example button link: `/cloud/subscribe?tier=standard`

`tier` could be `standard`, `creator` or `pro`
`cycle` could be `monthly` or `yearly`. it is optional, and `monthly` by
default.

<!-- One sentence describing what changed and why. -->

## Changes

- **What**: <!-- Core functionality added/modified -->
- Add a landing page called `CloudSubscriptionRedirectView.vue` to
handling the subscription tier button link parameter
  - Extract subscription handling logic from `PriceTable.vue`
 
- **Breaking**: <!-- Any breaking changes (if none, remove this line)
-->
  - Code change touched  `PriceTable.vue`
- **Dependencies**: <!-- New dependencies (if none, remove this line)
-->

## Review Focus
- link will redirect to login url, when cloud app not login
- after login, the cloud app will redirect to CloudSubscriptionRedirect
page
- wait for several seconds, the cloud app will be redirected to checkout
page

<!-- Critical design decisions or edge cases that need attention -->

<!-- If this PR fixes an issue, uncomment and update the line below -->
<!-- Fixes #ISSUE_NUMBER -->

## Screenshots (if applicable)

![Kapture 2025-12-16 at 18 43
28](https://github.com/user-attachments/assets/affbc18f-d45c-4953-b06a-fc797eba6804)


<!-- Add screenshots or video recording to help explain your changes -->

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7553-feat-handling-subscription-tier-button-link-parameter-2cb6d73d365081ee9580e89090248300)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>

src/composables/auth/useFirebaseAuthActions.ts

@@ -104,9 +104,9 @@ export const useFirebaseAuthActions = () => {
   }, reportError)
 
   const accessBillingPortal = wrapWithErrorHandlingAsync<
-    [targetTier?: BillingPortalTargetTier],
+    [targetTier?: BillingPortalTargetTier, openInNewTab?: boolean],
     void
-  >(async (targetTier) => {
+  >(async (targetTier, openInNewTab = true) => {
     const response = await authStore.accessBillingPortal(targetTier)
     if (!response.billing_portal_url) {
       throw new Error(
@@ -115,7 +115,11 @@ export const useFirebaseAuthActions = () => {
         })
       )
     }
-    window.open(response.billing_portal_url, '_blank')
+    if (openInNewTab) {
+      window.open(response.billing_portal_url, '_blank')
+    } else {
+      globalThis.location.href = response.billing_portal_url
+    }
   }, reportError)
 
   const fetchBalance = wrapWithErrorHandlingAsync(async () => {