Add overdue invoices check (#31290)

- Rename current_user_account_too_young to account_too_young for
consistency
- Add has_overdue_invoices field to track billing status
- Block edit predictions when user has overdue invoices
- Add overdue invoice warning to inline completion menu

Release Notes:

- N/A

---------

Co-authored-by: Marshall Bowers <git@maxdeviant.com>

crates/agent/src/agent_panel.rs

@@ -1973,7 +1973,7 @@ impl AgentPanel {
             return None;
         }
 
-        if self.user_store.read(cx).current_user_account_too_young() {
+        if self.user_store.read(cx).account_too_young() {
             Some(self.render_young_account_upsell(cx).into_any_element())
         } else {
             Some(self.render_trial_upsell(cx).into_any_element())