feat(frontend): add MCP import dialog for v3.7.0

Implement import functionality to migrate MCP servers from existing configs:

**New Component:**
- src/components/mcp/McpImportDialog.tsx: Import dialog with card-based source selection

**Features:**
- Import from Claude (~/.claude/claude.json or settings.json)
- Import from Codex (~/.codex/config.toml)
- Import from Gemini (config file)
- Card-based UI with icons and descriptions
- Loading states with spinner animation
- Auto-refresh after successful import

**Integration:**
- Add import button to UnifiedMcpPanel header
- Handle import completion with refetch
- Toast notifications for success/info/error cases

**I18n:**
- Add mcp.unifiedPanel.import namespace (zh/en)
- Import button, dialog title, descriptions
- Success/error messages with count interpolation

**UX:**
- Smart disable: other sources disabled during import
- Clear feedback: count of imported servers
- Friendly messages: "No servers found" when empty

TypeScript type check passes ✅

src/components/mcp/UnifiedMcpPanel.tsx

@@ -1,6 +1,6 @@
 import React, { useMemo, useState } from "react";
 import { useTranslation } from "react-i18next";
-import { Plus, Server, Check, RefreshCw } from "lucide-react";
+import { Plus, Server, Check, RefreshCw, Download } from "lucide-react";
 import { Button } from "@/components/ui/button";
 import {
   Dialog,
@@ -14,6 +14,7 @@ import { useAllMcpServers, useToggleMcpApp, useSyncAllMcpServers } from "@/hooks
 import type { McpServer } from "@/types";
 import type { AppId } from "@/lib/api/types";
 import McpFormModal from "./McpFormModal";
+import McpImportDialog from "./McpImportDialog";
 import { ConfirmDialog } from "../ConfirmDialog";
 import { useDeleteMcpServer } from "@/hooks/useMcp";
 import { Edit3, Trash2 } from "lucide-react";
@@ -36,6 +37,7 @@ const UnifiedMcpPanel: React.FC<UnifiedMcpPanelProps> = ({
 }) => {
   const { t } = useTranslation();
   const [isFormOpen, setIsFormOpen] = useState(false);
+  const [isImportOpen, setIsImportOpen] = useState(false);
   const [editingId, setEditingId] = useState<string | null>(null);
   const [confirmDialog, setConfirmDialog] = useState<{
     isOpen: boolean;
@@ -45,7 +47,7 @@ const UnifiedMcpPanel: React.FC<UnifiedMcpPanelProps> = ({
   } | null>(null);
 
   // Queries and Mutations
-  const { data: serversMap, isLoading } = useAllMcpServers();
+  const { data: serversMap, isLoading, refetch } = useAllMcpServers();
   const toggleAppMutation = useToggleMcpApp();
   const deleteServerMutation = useDeleteMcpServer();
   const syncAllMutation = useSyncAllMcpServers();
@@ -126,6 +128,11 @@ const UnifiedMcpPanel: React.FC<UnifiedMcpPanelProps> = ({
     setEditingId(null);
   };
 
+  const handleImportComplete = () => {
+    // Refresh the servers list after import
+    refetch();
+  };
+
   return (
     <>
       <Dialog open={open} onOpenChange={onOpenChange}>
@@ -134,6 +141,15 @@ const UnifiedMcpPanel: React.FC<UnifiedMcpPanelProps> = ({
             <div className="flex items-center justify-between pr-8">
               <DialogTitle>{t("mcp.unifiedPanel.title")}</DialogTitle>
               <div className="flex gap-2">
+                <Button
+                  type="button"
+                  variant="outline"
+                  size="sm"
+                  onClick={() => setIsImportOpen(true)}
+                >
+                  <Download size={16} />
+                  {t("mcp.unifiedPanel.import.button")}
+                </Button>
                 <Button
                   type="button"
                   variant="outline"
@@ -231,6 +247,13 @@ const UnifiedMcpPanel: React.FC<UnifiedMcpPanelProps> = ({
         />
       )}
 
+      {/* Import Dialog */}
+      <McpImportDialog
+        open={isImportOpen}
+        onOpenChange={setIsImportOpen}
+        onImportComplete={handleImportComplete}
+      />
+
       {/* Confirm Dialog */}
       {confirmDialog && (
         <ConfirmDialog