refactor(mcp): redesign MCP management panel UI

- Redesign MCP panel to match main interface style
- Add toggle switch for each MCP server to enable/disable
- Use emerald theme color consistent with MCP button
- Create card-based layout with one MCP per row
- Add dedicated form modal for add/edit operations
- Implement proper empty state with friendly prompts
- Add comprehensive i18n support (zh/en)
- Extend McpServer type to support enabled field
- Backend already supports enabled field via serde_json::Value

Components:
- McpPanel: Main panel container with header and list
- McpListItem: Card-based list item with toggle and actions
- McpFormModal: Independent modal for add/edit forms
- McpToggle: Emerald-themed toggle switch component

All changes passed TypeScript type checking and production build.

src/i18n/locales/en.json

@@ -8,6 +8,7 @@
     "edit": "Edit",
     "delete": "Delete",
     "save": "Save",
+    "saving": "Saving...",
     "cancel": "Cancel",
     "confirm": "Confirm",
     "close": "Close",
@@ -255,9 +256,12 @@
     "serverList": "Servers",
     "loading": "Loading...",
     "empty": "No MCP servers",
-    "add": "Add Server",
+    "emptyDescription": "Click the button in the top right to add your first MCP server",
+    "add": "Add MCP",
     "addServer": "Add Server",
     "editServer": "Edit Server",
+    "configPath": "Config Path",
+    "serverCount": "{{count}} MCP server(s) configured",
     "template": {
       "fetch": "Quick Template: mcp-fetch"
     },
@@ -277,6 +281,8 @@
     "msg": {
       "saved": "Saved",
       "deleted": "Deleted",
+      "enabled": "Enabled",
+      "disabled": "Disabled",
       "templateAdded": "Template added"
     },
     "error": {
@@ -288,6 +294,10 @@
     "validation": {
       "ok": "Command available",
       "fail": "Command not found"
+    },
+    "confirm": {
+      "deleteTitle": "Delete MCP Server",
+      "deleteMessage": "Are you sure you want to delete MCP server \"{{id}}\"? This action cannot be undone."
     }
   }
 }