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/components/dialog/content/setting/UserPanel.vue

@@ -63,14 +63,18 @@
             <i class="pi pi-sign-out" />
             {{ $t('auth.signOut.signOut') }}
           </Button>
-          <Button
+          <i18n-t
             v-if="!isApiKeyLogin"
-            class="w-fit"
-            variant="destructive-textonly"
-            @click="handleDeleteAccount"
+            keypath="auth.deleteAccount.contactSupport"
+            tag="p"
+            class="text-muted text-sm"
           >
-            {{ $t('auth.deleteAccount.deleteAccount') }}
-          </Button>
+            <template #email>
+              <a href="mailto:support@comfy.org" class="underline"
+                >support@comfy.org</a
+              >
+            </template>
+          </i18n-t>
         </div>
       </div>
 
@@ -116,7 +120,6 @@ const {
   providerName,
   providerIcon,
   handleSignOut,
-  handleSignIn,
-  handleDeleteAccount
+  handleSignIn
 } = useCurrentUser()
 </script>