refactor: start on removing FF for subscription tiers (#7596)

## Summary

Refactor: remove FF for subscription tier, remove legacy code for non
subscription tier logic.
 
## Review Focus

Preexisting cloud functionality impact.

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

## Screenshots (if applicable)

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┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7596-refactor-start-on-removing-FF-for-subscription-tiers-2cc6d73d3650816bac3aef893e4f37cd)
by [Unito](https://www.unito.io)

src/platform/cloud/subscription/components/SubscribeButton.vue

@@ -26,7 +26,6 @@
 import Button from 'primevue/button'
 import { computed, onBeforeUnmount, ref, watch } from 'vue'
 
-import { useFeatureFlags } from '@/composables/useFeatureFlags'
 import { useSubscription } from '@/platform/cloud/subscription/composables/useSubscription'
 import { isCloud } from '@/platform/distribution/types'
 import { useTelemetry } from '@/platform/telemetry'
@@ -54,10 +53,7 @@ const emit = defineEmits<{
 
 const { subscribe, isActiveSubscription, fetchStatus, showSubscriptionDialog } =
   useSubscription()
-const { flags } = useFeatureFlags()
-const shouldUseStripePricing = computed(
-  () => isCloud && Boolean(flags.subscriptionTiersEnabled)
-)
+
 const telemetry = useTelemetry()
 
 const isLoading = ref(false)
@@ -112,7 +108,7 @@ const stopPolling = () => {
 watch(
   [isAwaitingStripeSubscription, isActiveSubscription],
   ([awaiting, isActive]) => {
-    if (shouldUseStripePricing.value && awaiting && isActive) {
+    if (isCloud && awaiting && isActive) {
       emit('subscribed')
       isAwaitingStripeSubscription.value = false
     }
@@ -122,9 +118,6 @@ watch(
 const handleSubscribe = async () => {
   if (isCloud) {
     useTelemetry()?.trackSubscription('subscribe_clicked')
-  }
-
-  if (shouldUseStripePricing.value) {
     isAwaitingStripeSubscription.value = true
     showSubscriptionDialog()
     return

src/platform/cloud/subscription/composables/useSubscription.ts

@@ -16,9 +16,9 @@ import { useDialogService } from '@/services/dialogService'
 import type { components, operations } from '@/types/comfyRegistryTypes'
 import { useSubscriptionCancellationWatcher } from './useSubscriptionCancellationWatcher'
 
-type CloudSubscriptionCheckoutResponse = {
-  checkout_url: string
-}
+type CloudSubscriptionCheckoutResponse = NonNullable<
+  operations['createCloudSubscriptionCheckout']['responses']['201']['content']['application/json']
+>
 
 export type CloudSubscriptionStatusResponse = NonNullable<
   operations['GetCloudSubscriptionStatus']['responses']['200']['content']['application/json']