fix: Conditionally fetch limits and assistants for enterprise/cloud (#12099)

# Pull Request Template

## Description

### Issue

The Community Edition (CE) dashboard was making API requests to
enterprise-only endpoints, causing 404 errors:

* `/enterprise/api/v1/accounts/1/limits`
* `/api/v1/accounts/1/captain/assistants?page=1`

### Solution

1. Added conditional checks to prevent these calls.
2. Remove unused component
`app/javascript/dashboard/components/app/UpgradeBanner.vue`

Fixes
[CW-4695](https://linear.app/chatwoot/issue/CW-4695/440-ce-dashboard-calls-enterprise-urls),
https://github.com/chatwoot/chatwoot/issues/12023

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Pranav <pranavrajs@gmail.com>

app/javascript/dashboard/routes/dashboard/upgrade/UpgradePage.vue

@@ -4,6 +4,7 @@ import { useStore } from 'dashboard/composables/store';
 import { useMapGetter } from 'dashboard/composables/store.js';
 import { useRouter } from 'vue-router';
 import { useAccount } from 'dashboard/composables/useAccount';
+import { useConfig } from 'dashboard/composables/useConfig';
 import { differenceInDays } from 'date-fns';
 import { useAdmin } from 'dashboard/composables/useAdmin';
 import { useI18n } from 'vue-i18n';
@@ -22,6 +23,7 @@ const router = useRouter();
 const store = useStore();
 const { t } = useI18n();
 const { accountId, currentAccount } = useAccount();
+const { isEnterprise } = useConfig();
 const { isAdmin } = useAdmin();
 
 const isOnChatwootCloud = useMapGetter('globalConfig/isOnChatwootCloud');
@@ -100,7 +102,11 @@ const routeToBilling = () => {
   });
 };
 
-onMounted(() => fetchLimits());
+onMounted(() => {
+  if (isEnterprise) {
+    fetchLimits();
+  }
+});
 
 defineExpose({ shouldShowUpgradePage });
 </script>