fix: throttle sign-up and sign-in button (#7358)

## Summary

<!-- One sentence describing what changed and why. -->
Throttle signup button to prevent duplicate Firebase accounts

## Changes

- **What**: <!-- Core functionality added/modified -->
  - Add throttle to SignUp Button in SignUpForm component
  - Add throttle to SignIn Button in SignInForm component
  - Add loading state to SignUp Button in SignUpForm component

## Review Focus
related to this Notion page:
https://www.notion.so/comfy-org/Implement-Throttle-signup-button-to-prevent-duplicate-Firebase-accounts-2c46d73d36508193a8d1fb5146674956

<!-- 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)

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

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7358-fix-throttle-sign-up-and-sign-in-button-2c66d73d365081278f4dde0f34d60153)
by [Unito](https://www.unito.io)

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

@@ -59,7 +59,7 @@ function useSubscriptionInternal() {
 
     const renewalDate = new Date(subscriptionStatus.value.renewal_date)
 
-    return renewalDate.toLocaleDateString(undefined, {
+    return renewalDate.toLocaleDateString('en-US', {
       month: 'short',
       day: 'numeric',
       year: 'numeric'
@@ -71,7 +71,7 @@ function useSubscriptionInternal() {
 
     const endDate = new Date(subscriptionStatus.value.end_date)
 
-    return endDate.toLocaleDateString(undefined, {
+    return endDate.toLocaleDateString('en-US', {
       month: 'short',
       day: 'numeric',
       year: 'numeric'