feat(skills): add install from ZIP file feature

- Add open_zip_file_dialog command for selecting ZIP files
- Add install_from_zip service method with recursive skill scanning
- Add install_skills_from_zip Tauri command
- Add frontend API methods and useInstallSkillsFromZip hook
- Add "Install from ZIP" button in Skills management page
- Support local skill ID format: local:{directory}
- Add i18n translations for new feature and error messages

src/lib/api/index.ts

@@ -3,6 +3,7 @@ export { providersApi, universalProvidersApi } from "./providers";
 export { settingsApi } from "./settings";
 export { mcpApi } from "./mcp";
 export { promptsApi } from "./prompts";
+export { skillsApi } from "./skills";
 export { usageApi } from "./usage";
 export { vscodeApi } from "./vscode";
 export { proxyApi } from "./proxy";