chore: add Biome for lint and fix all lint errors

- Install @biomejs/biome as devDependency at root
- Configure biome.json with 2-space indent, double quotes, Tailwind CSS support
- Add lint/lint:fix/format/format:fix scripts to root and app package.json
- Fix noNonNullAssertion: env vars extracted to variables with suppression, <div role=button> replaced with <button>
- Fix noUnusedVariables: remove unused destructured vars
- Fix useIterableCallbackReturn: arrow functions with block body
- Fix noExplicitAny: recharts Tooltip formatters
- Fix noLabelWithoutControl: add htmlFor+id or use <span> for non-input labels
- Fix noStaticElementInteractions/useKeyWithClickEvents: role+keyboard events for overlays
- Fix noArrayIndexKey: use error string as key
- Fix CSS parse: enable tailwindDirectives parser
- Normalize formatting across 80 files with biome check --write

apps/frontend/src/components/layout/Layout.tsx

@@ -1,8 +1,8 @@
-import { useState } from "react";
 import { Outlet } from "@tanstack/react-router";
+import { useState } from "react";
+import { LoadingBar } from "@/components/ui/loading-bar";
 import { Header } from "./Header";
 import { Sidebar } from "./Sidebar";
-import { LoadingBar } from "@/components/ui/loading-bar";
 
 export function Layout() {
   const [sidebarOpen, setSidebarOpen] = useState(false);