fix: eslint findings

Remove dead code and unused imports, drop useless assignments, and tune
rules in eslint.config.js (underscore-prefixed unused names, intentional BOM/NBSP,
React Compiler rules from eslint-plugin-react-hooks 7 as warnings).

src/views/AppSettings.tsx

@@ -24,7 +24,6 @@ import {
   TabPanels,
   Tabs,
   Tile,
-  Toggle,
 } from "@carbon/react";
 import { Add, Save, TrashCan } from "@carbon/icons-react";
 import { confirm } from "@tauri-apps/plugin-dialog";