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/platform/cloud/onboarding/CloudSignupView.vue

@@ -100,6 +100,7 @@ import { useRoute, useRouter } from 'vue-router'
 import SignUpForm from '@/components/dialog/content/signin/SignUpForm.vue'
 import Button from '@/components/ui/button/Button.vue'
 import { useFirebaseAuthActions } from '@/composables/auth/useFirebaseAuthActions'
+import { getSafePreviousFullPath } from '@/platform/cloud/onboarding/utils/previousFullPath'
 import { isCloud } from '@/platform/distribution/types'
 import { useTelemetry } from '@/platform/telemetry'
 import { useToastStore } from '@/platform/updates/common/toastStore'
@@ -110,13 +111,13 @@ const { t } = useI18n()
 const router = useRouter()
 const route = useRoute()
 const authActions = useFirebaseAuthActions()
-const isSecureContext = window.isSecureContext
+const isSecureContext = globalThis.isSecureContext
 const authError = ref('')
 const userIsInChina = ref(false)
 const toastStore = useToastStore()
 
-const navigateToLogin = () => {
-  void router.push({ name: 'cloud-login', query: route.query })
+const navigateToLogin = async () => {
+  await router.push({ name: 'cloud-login', query: route.query })
 }
 
 const onSuccess = async () => {
@@ -125,7 +126,14 @@ const onSuccess = async () => {
     summary: 'Sign up Completed',
     life: 2000
   })
-  // Direct redirect to main app - email verification removed
+
+  const previousFullPath = getSafePreviousFullPath(route.query)
+  if (previousFullPath) {
+    await router.replace(previousFullPath)
+    return
+  }
+
+  // Default redirect to the normal onboarding flow
   await router.push({ path: '/', query: route.query })
 }