feat: invite member upsell for single-seat plans (#8801)

## Summary

- Show an upsell dialog when single-seat plan users try to invite
members, with a banner on the members panel directing them to upgrade.
- Misc fixes for member max seat display

## Changes

- **What**: `InviteMemberUpsellDialogContent.vue`,
`MembersPanelContent.vue`, `WorkspacePanelContent.vue`

## Screenshots

<img width="2730" height="1907" alt="image"
src="https://github.com/user-attachments/assets/e39a23be-8533-4ebb-a4ae-2797fc382bc2"
/>
<img width="2730" height="1907" alt="image"
src="https://github.com/user-attachments/assets/bec55867-1088-4d3a-b308-5d5cce64c8ae"
/>



┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8801-feat-invite-member-upsell-for-single-seat-plans-3046d73d365081349b09fe1d4dc572e8)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: GitHub Action <action@github.com>

src/services/dialogService.ts

@@ -711,6 +711,22 @@ export const useDialogService = () => {
     })
   }
 
+  async function showInviteMemberUpsellDialog() {
+    const { default: component } =
+      await import('@/components/dialog/content/workspace/InviteMemberUpsellDialogContent.vue')
+    return dialogStore.showDialog({
+      key: 'invite-member-upsell',
+      component,
+      dialogComponentProps: {
+        ...workspaceDialogPt,
+        pt: {
+          ...workspaceDialogPt.pt,
+          root: { class: 'rounded-2xl max-w-[512px] w-full' }
+        }
+      }
+    })
+  }
+
   async function showRevokeInviteDialog(inviteId: string) {
     const { default: component } =
       await import('@/components/dialog/content/workspace/RevokeInviteDialogContent.vue')
@@ -782,6 +798,7 @@ export const useDialogService = () => {
     showRemoveMemberDialog,
     showRevokeInviteDialog,
     showInviteMemberDialog,
+    showInviteMemberUpsellDialog,
     showBillingComingSoonDialog,
     showCancelSubscriptionDialog
   }