fix: 注册表单仅输入区域滚动，暗色主题输入框颜色优化

- 注册Tab结构: Text(固定) + VScrollPanel(仅Form) + Button(固定)
- 暗色主题输入框背景 #0f172a -> #1e293b，更协调

wwwroot/login.css

@@ -217,7 +217,7 @@
 	border-bottom-color: #818cf8 !important;
 }
 [data-theme="dark"] .login-window .inputbox {
-	background: #0f172a !important;
+	background: #1e293b !important;
 	border-color: #475569 !important;
 	color: #e2e8f0 !important;
 }

wwwroot/user/login.ui

@@ -121,12 +121,8 @@
                         "name": "register",
                         "label": "注册账号",
                         "content": {
-                            "widgettype": "VScrollPanel",
-                            "options": {"height": "100%"},
-                            "subwidgets": [
-                                {
                             "widgettype": "VBox",
-                                    "options": {"gap": "8px"},
+                            "options": {"gap": "8px", "height": "100%"},
                             "subwidgets": [
                                 {
                                     "widgettype": "Text",
@@ -136,6 +132,10 @@
                                         "css": "login-desc"
                                     }
                                 },
+                                {
+                                    "widgettype": "VScrollPanel",
+                                    "options": {"height": "100%", "flex": "1"},
+                                    "subwidgets": [
                                         {
                                             "widgettype": "Form",
                                             "id": "register_form",
@@ -162,6 +162,8 @@
                                                     }
                                                 }
                                             ]
+                                        }
+                                    ]
                                 },
                                 {
                                     "widgettype": "Button",
@@ -179,8 +181,6 @@
                                 }
                             ]
                         }
-                            ]
-                        }
                     }
                 ]
             }