feat(mcp): add import button to import MCP servers from apps

- Add import_mcp_from_apps command that reuses existing import logic
- Add Import button in MCP panel header (consistent with Skills)
- Fix import count to only return truly new servers (not already in DB)
- Update translations for import success/no-import messages (zh/en/ja)

src-tauri/src/lib.rs

@@ -637,6 +637,7 @@ pub fn run() {
             commands::upsert_mcp_server,
             commands::delete_mcp_server,
             commands::toggle_mcp_app,
+            commands::import_mcp_from_apps,
             // Prompt management
             commands::get_prompts,
             commands::upsert_prompt,