Evergreen farms (pos)

h3. Fix & Implementation Summary for Bug #11834

• Backend User Creation Limit Enforcement (`user-controller.js`, `tenantUsage.service.js`):
  - Integrated `tenantUsageService.checkLimit(dbName, "users", 1)` into the user creation lifecycle (`createUser`, `updateUser`).
  - Added strict guardrail checks: when a tenant reaches their allocated user quota (`maxUsers`), further user creations are intercepted and blocked with a `403 Forbidden` response.
  - Ensured active user count synchronization (`syncUserCount`) counts only non-deleted users from the tenant's database.

• Quota Alert & Threshold Engine (`tenantBilling.service.js`):
  - Added real-time usage calculation across metered resources (`Users`, `Stores`, `SMS`, `Email`).
  - Implemented severity-based alert rules returned in the tenant billing summary: * Warning Alert (>= 80% usage): Alert notifying that the quota is nearing capacity (e.g. `User accounts is near capacity (X/Y - Z% used)`). * Critical Alert (>= 100% usage): High-priority alert notifying that the resource limit has been reached and new creations are blocked.

• Admin Dashboard & Global Banner UI (`SalesDashboard.tsx`, `PlanExpiryBanner.tsx`):
  - Admin Sales Dashboard: Added the `🚨 Resource Quota Alert` banner that renders directly at the top of the dashboard when any metric is near or at limit, showing the exact metric counts and an direct `"Upgrade / Top-Up Now"` button linking to `/settings/plan-usage`.
  - Global Sticky Banner: Added critical limit warnings to `PlanExpiryBanner.tsx` so tenant administrators are notified of resource exhaustion across all views.
  - Plan Usage Page: Added real-time usage tracking meters and upgrade/top-up flows.