Add server status monitoring endpoint

- Add status.service.js with CPU, RAM, Disk, Backend stats
- RAM calculation matches htop (reads /proc/meminfo)
- Includes uploads folder size, DB table count
- Returns both system and backend (process) uptime

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/controllers/admin.controller.js

@@ -1,4 +1,5 @@
 import * as adminService from '../services/admin.service.js';
+import * as statusService from '../services/status.service.js';
 import { logUserCreation, logRoleChange } from '../services/audit.service.js';
 
 /**
@@ -142,3 +143,20 @@ export const deleteUser = async (req, res, next) => {
     return next(error);
   }
 };
+
+/**
+ * Get server status (admin only)
+ * GET /api/admin/server-status
+ */
+export const getServerStatus = async (req, res, next) => {
+  try {
+    const status = await statusService.getServerStatus();
+
+    res.status(200).json({
+      success: true,
+      data: status,
+    });
+  } catch (error) {
+    return next(error);
+  }
+};