fix(login): mueve login a /pos/login2 para evitar cache viejo

- /pos/login redirige a /pos/login2 (no-store).
- /pos/login2 sirve la plantilla actualizada que envia employee_id.
- nginx redirige / a /pos/login2.

Esto evita que navegadores/PWA con cache antigua sigan usando la version
que no enviaba el empleado seleccionado.

pos/app.py

@@ -144,15 +144,15 @@ def create_app():
         return send_from_directory('static/pwa', 'icon-192.png', mimetype='image/png')
 
     @app.route('/pos/login')
-    def pos_login():
-        # Bust browser cache by always serving the login page under a versioned URL.
-        if request.args.get('v') != '34':
-            response = make_response(redirect('/pos/login?v=34'))
-            response.headers['Cache-Control'] = 'no-store, no-cache, must-revalidate, max-age=0'
-            response.headers['Pragma'] = 'no-cache'
-            response.headers['Expires'] = '0'
-            return response
+    def pos_login_legacy():
+        # Redirect to the new login path to bypass any stale browser/SW cache
+        # of the old /pos/login page that did not send employee_id.
+        response = make_response(redirect('/pos/login2'))
+        response.headers['Cache-Control'] = 'no-store, no-cache, must-revalidate, max-age=0'
+        return response
 
+    @app.route('/pos/login2')
+    def pos_login():
         response = make_response(render_template('login.html',
                                tenant_id=getattr(g, 'tenant_id', None),
                                tenant_name=getattr(g, 'tenant_name', None),