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/Header.tsx

@@ -1,8 +1,8 @@
-import { Menu, Sun, Moon, Monitor, LogOut } from "lucide-react";
+import { LogOut, Menu, Monitor, Moon, Sun } from "lucide-react";
 import { Button } from "@/components/ui/button";
+import { useAuth } from "@/lib/auth-context";
 import { useSseStatus } from "@/lib/sse-context";
 import { useTheme } from "@/lib/theme";
-import { useAuth } from "@/lib/auth-context";
 import { cn } from "@/lib/utils";
 
 interface HeaderProps {

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);

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

@@ -1,5 +1,11 @@
 import { Link } from "@tanstack/react-router";
-import { FileText, LayoutDashboard, Settings, TrendingUp, Wallet } from "lucide-react";
+import {
+  FileText,
+  LayoutDashboard,
+  Settings,
+  TrendingUp,
+  Wallet,
+} from "lucide-react";
 import { cn } from "@/lib/utils";
 
 const navItems = [
@@ -22,9 +28,11 @@ export function Sidebar({ open, onClose }: SidebarProps) {
   return (
     <>
       {open && (
-        <div
-          className="fixed inset-0 z-40 bg-black/20 md:hidden"
+        <button
+          type="button"
+          className="fixed inset-0 z-40 bg-black/20 md:hidden cursor-default"
           onClick={onClose}
+          aria-label="Cerrar menú"
         />
       )}
       <aside
@@ -43,7 +51,10 @@ export function Sidebar({ open, onClose }: SidebarProps) {
             <Link
               key={item.to}
               to={item.to}
-              activeProps={{ className: "bg-sidebar-accent text-sidebar-accent-foreground font-medium" }}
+              activeProps={{
+                className:
+                  "bg-sidebar-accent text-sidebar-accent-foreground font-medium",
+              }}
               className="flex items-center gap-3 rounded-lg px-3 py-2 text-sm text-sidebar-foreground/70 transition-colors hover:bg-sidebar-accent hover:text-sidebar-accent-foreground"
               onClick={onClose}
             >
@@ -57,7 +68,10 @@ export function Sidebar({ open, onClose }: SidebarProps) {
             <Link
               key={item.to}
               to={item.to}
-              activeProps={{ className: "bg-sidebar-accent text-sidebar-accent-foreground font-medium" }}
+              activeProps={{
+                className:
+                  "bg-sidebar-accent text-sidebar-accent-foreground font-medium",
+              }}
               className="flex items-center gap-3 rounded-lg px-3 py-2 text-sm text-sidebar-foreground/70 transition-colors hover:bg-sidebar-accent hover:text-sidebar-accent-foreground"
               onClick={onClose}
             >