Revert "Refactor login method to use unified identifier for user input; update request body to support both email and username"

This reverts commit 3c901a35a6.

src/services/auth.js

@@ -4,19 +4,14 @@ export class Auth {
     this.isAuthenticated = false;
   }
 
-  async login(identifier, password) {
-    if (!identifier || !password) return false;
+  async login(email, password) {
+    if (!email || !password) return false;
 
     try {
       const response = await fetch(`${import.meta.env.VITE_API_BASE_URL}/api/Auth/login`, {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
-        // Enviamos ambos nombres de campo para cubrir email o userName según espere el backend.
-        body: JSON.stringify({
-          email: identifier,
-          userName: identifier,
-          password
-        })
+        body: JSON.stringify({ email, password })
       });
 
       if (!response.ok) return false;
@@ -24,7 +19,7 @@ export class Auth {
       const { token, user } = await response.json();
       if (!token) return false;
 
-      this.currentUser = user || { email: identifier };
+      this.currentUser = user || { email };
       this.isAuthenticated = true;
       localStorage.setItem('user', JSON.stringify(this.currentUser));
       localStorage.setItem('token', token);