Add virtual model support for multi-key expansion

Virtual models generated from multi-key expansion are now marked and
filtered during config persistence. Virtual models display with a badge
in the UI and cannot be set as default.

web/frontend/src/i18n/locales/en.json

@@ -154,7 +154,8 @@
       "unconfigured": "Not configured"
     },
     "badge": {
-      "default": "Default"
+      "default": "Default",
+      "virtual": "Virtual"
     },
     "action": {
       "edit": "Edit API key",

web/frontend/src/i18n/locales/zh.json

@@ -154,7 +154,8 @@
       "unconfigured": "未配置"
     },
     "badge": {
-      "default": "默认"
+      "default": "默认",
+      "virtual": "虚拟"
     },
     "action": {
       "edit": "编辑 API Key",