fix: resolve login persistence bug and aggressive logout on network blips

- Updated Login.tsx to automatically redirect users to the dashboard if a valid token is already present in localStorage.

- Refactored getUserById to properly throw server/network errors instead of silently returning undefined.

- Updated AuthGuard in App.tsx to gracefully handle network errors without destroying the user's valid localStorage tokens.

pages/Login.tsx

@@ -1,4 +1,4 @@
-import React, { useState } from 'react';
+import React, { useState, useEffect } from 'react';
 import { useNavigate, Link } from 'react-router-dom';
 import { Hexagon, Lock, Mail, ArrowRight, Loader2, Eye, EyeOff, AlertCircle } from 'lucide-react';
 import { login, logout } from '../services/dataService';
@@ -12,6 +12,16 @@ export const Login: React.FC = () => {
   const [error, setError] = useState('');
   const [emailError, setEmailError] = useState('');
 
+  // Auto-redirect if already logged in
+  useEffect(() => {
+    const token = localStorage.getItem('ctms_token');
+    const userId = localStorage.getItem('ctms_user_id');
+    if (token && userId && token !== 'undefined' && token !== 'null') {
+      // Opt to send them to root, AuthGuard will handle role-based routing
+      navigate('/');
+    }
+  }, [navigate]);
+
   const validateEmail = (val: string) => {
     setEmail(val);
     if (!val) {