fix: remove delete account button and direct users to support (#8515)

## Summary
Reverts PR #5216 delete account functionality. The delete button only
removed Firebase accounts without canceling Stripe subscriptions,
causing orphaned accounts and support issues.

## Changes
- Removed delete account button from UserPanel.vue
- Added text directing users to contact support@comfy.org for account
deletion (clickable mailto: link)
- Cleaned up related code: removed `handleDeleteAccount` from
useCurrentUser.ts, `deleteAccount` from useFirebaseAuthActions.ts,
`_deleteAccount` from firebaseAuthStore.ts
- Updated en/main.json locale with `contactSupport` key using {email}
placeholder

## Testing
- Typecheck and lint pass
- Manual verification: user settings panel shows contact support text
instead of delete button

## Related Issues
Fixes COM-14243

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8515-fix-remove-delete-account-button-and-direct-users-to-support-2fa6d73d3650819dbc83efb41c07a809)
by [Unito](https://www.unito.io)

Co-authored-by: Amp <amp@ampcode.com>

src/stores/firebaseAuthStore.ts

@@ -5,7 +5,6 @@ import {
   GoogleAuthProvider,
   browserLocalPersistence,
   createUserWithEmailAndPassword,
-  deleteUser,
   getAdditionalUserInfo,
   onAuthStateChanged,
   onIdTokenChanged,
@@ -429,14 +428,6 @@ export const useFirebaseAuthStore = defineStore('firebaseAuth', () => {
     await updatePassword(currentUser.value, newPassword)
   }
 
-  /** Delete the current user account */
-  const _deleteAccount = async (): Promise<void> => {
-    if (!currentUser.value) {
-      throw new FirebaseAuthStoreError(t('toastMessages.userNotAuthenticated'))
-    }
-    await deleteUser(currentUser.value)
-  }
-
   const addCredits = async (
     requestBodyContent: CreditPurchasePayload
   ): Promise<CreditPurchaseResponse> => {
@@ -536,7 +527,6 @@ export const useFirebaseAuthStore = defineStore('firebaseAuth', () => {
     accessBillingPortal,
     sendPasswordReset,
     updatePassword: _updatePassword,
-    deleteAccount: _deleteAccount,
     getAuthHeader,
     getFirebaseAuthHeader,
     getAuthToken