Feat/workspaces 6 billing (#8508)

## Summary

Implements billing infrastructure for team workspaces, separate from
legacy personal billing.

## Changes

- **Billing abstraction**: New `useBillingContext` composable that
switches between legacy (personal) and workspace billing based on
context
- **Workspace subscription flows**: Pricing tables, plan transitions,
cancellation dialogs, and payment preview components for workspace
billing
- **Top-up credits**: Workspace-specific top-up dialog with polling for
payment confirmation
- **Workspace API**: Extended with billing endpoints (subscriptions,
invoices, payment methods, credits top-up)
- **Workspace switcher**: Now displays tier badges for each workspace
- **Subscribe polling**: Added polling mechanisms
(`useSubscribePolling`, `useTopupPolling`) for async payment flows

## Review Focus

- Billing flow correctness for workspace vs legacy contexts
- Polling timeout and error handling in payment flows

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8508-Feat-workspaces-6-billing-2f96d73d365081f69f65c1ddf369010d)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

src/scripts/app.ts

@@ -50,7 +50,7 @@ import {
   DOMWidgetImpl
 } from '@/scripts/domWidget'
 import { useDialogService } from '@/services/dialogService'
-import { useSubscription } from '@/platform/cloud/subscription/composables/useSubscription'
+import { useBillingContext } from '@/composables/billing/useBillingContext'
 import { useExtensionService } from '@/services/extensionService'
 import { useLitegraphService } from '@/services/litegraphService'
 import { useSubgraphService } from '@/services/subgraphService'
@@ -687,7 +687,7 @@ export class ComfyApp {
           'Payment Required: Please add credits to your account to use this node.'
         )
       ) {
-        const { isActiveSubscription } = useSubscription()
+        const { isActiveSubscription } = useBillingContext()
         if (isActiveSubscription.value) {
           useDialogService().showTopUpCreditsDialog({
             isInsufficientCredits: true