feat: setup full Next.js toolchain and core dependencies

- Add runtime deps: react-query, react-hook-form+zod, zustand, ky, openapi-fetch,
  better-auth, react-markdown, shiki, recharts, next-themes, nuqs, sonner, cmdk,
  vaul, embla-carousel-react, motion, date-fns, tailwind-merge, clsx, cva
- Add dev tooling: vitest, testing-library, playwright, prettier(+tailwind plugin),
  husky, lint-staged, jsdom
- Wire providers (QueryClient, Theme, NuqsAdapter, Tooltip, Sonner) into layout
- Add vitest/playwright/prettier configs + lint-staged pre-commit hook
- Add lib/query-client + lib/http (ky) helpers and sample unit test
- Fix react-hooks/set-state-in-effect lint errors (use-mobile useSyncExternalStore,
  carousel async init)
- Remove committed Next-generated types/ duplicates (regenerated under .next/types)

components/ui/item.tsx

@@ -0,0 +1,188 @@
+import * as React from "react";
+import { mergeProps } from "@base-ui/react/merge-props";
+import { useRender } from "@base-ui/react/use-render";
+import { cva, type VariantProps } from "class-variance-authority";
+import { cn } from "cn";
+
+import { Separator } from "@/components/ui/separator";
+
+function ItemGroup({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      role="list"
+      data-slot="item-group"
+      className={cn(
+        "group/item-group flex w-full flex-col gap-4 has-data-[size=sm]:gap-2.5 has-data-[size=xs]:gap-2",
+        className
+      )}
+      {...props}
+    />
+  );
+}
+
+function ItemSeparator({ className, ...props }: React.ComponentProps<typeof Separator>) {
+  return (
+    <Separator
+      data-slot="item-separator"
+      orientation="horizontal"
+      className={cn("my-2", className)}
+      {...props}
+    />
+  );
+}
+
+const itemVariants = cva(
+  "group/item flex w-full flex-wrap items-center rounded-lg border text-sm transition-colors duration-100 outline-none focus-visible:border-ring focus-visible:ring-[3px] focus-visible:ring-ring/50 [a]:transition-colors [a]:hover:bg-muted",
+  {
+    variants: {
+      variant: {
+        default: "border-transparent",
+        outline: "border-border",
+        muted: "border-transparent bg-muted/50",
+      },
+      size: {
+        default: "gap-2.5 px-3 py-2.5",
+        sm: "gap-2.5 px-3 py-2.5",
+        xs: "gap-2 px-2.5 py-2 in-data-[slot=dropdown-menu-content]:p-0",
+      },
+    },
+    defaultVariants: {
+      variant: "default",
+      size: "default",
+    },
+  }
+);
+
+function Item({
+  className,
+  variant = "default",
+  size = "default",
+  render,
+  ...props
+}: useRender.ComponentProps<"div"> & VariantProps<typeof itemVariants>) {
+  return useRender({
+    defaultTagName: "div",
+    props: mergeProps<"div">(
+      {
+        className: cn(itemVariants({ variant, size, className })),
+      },
+      props
+    ),
+    render,
+    state: {
+      slot: "item",
+      variant,
+      size,
+    },
+  });
+}
+
+const itemMediaVariants = cva(
+  "flex shrink-0 items-center justify-center gap-2 group-has-data-[slot=item-description]/item:translate-y-0.5 group-has-data-[slot=item-description]/item:self-start [&_svg]:pointer-events-none",
+  {
+    variants: {
+      variant: {
+        default: "bg-transparent",
+        icon: "[&_svg:not([class*='size-'])]:size-4",
+        image:
+          "size-10 overflow-hidden rounded-sm group-data-[size=sm]/item:size-8 group-data-[size=xs]/item:size-6 [&_img]:size-full [&_img]:object-cover",
+      },
+    },
+    defaultVariants: {
+      variant: "default",
+    },
+  }
+);
+
+function ItemMedia({
+  className,
+  variant = "default",
+  ...props
+}: React.ComponentProps<"div"> & VariantProps<typeof itemMediaVariants>) {
+  return (
+    <div
+      data-slot="item-media"
+      data-variant={variant}
+      className={cn(itemMediaVariants({ variant, className }))}
+      {...props}
+    />
+  );
+}
+
+function ItemContent({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="item-content"
+      className={cn(
+        "flex flex-1 flex-col gap-1 group-data-[size=xs]/item:gap-0 [&+[data-slot=item-content]]:flex-none",
+        className
+      )}
+      {...props}
+    />
+  );
+}
+
+function ItemTitle({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="item-title"
+      className={cn(
+        "line-clamp-1 flex w-fit items-center gap-2 text-sm leading-snug font-medium underline-offset-4",
+        className
+      )}
+      {...props}
+    />
+  );
+}
+
+function ItemDescription({ className, ...props }: React.ComponentProps<"p">) {
+  return (
+    <p
+      data-slot="item-description"
+      className={cn(
+        "line-clamp-2 text-left text-sm leading-normal font-normal text-muted-foreground group-data-[size=xs]/item:text-xs [&>a]:underline [&>a]:underline-offset-4 [&>a:hover]:text-primary",
+        className
+      )}
+      {...props}
+    />
+  );
+}
+
+function ItemActions({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div data-slot="item-actions" className={cn("flex items-center gap-2", className)} {...props} />
+  );
+}
+
+function ItemHeader({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="item-header"
+      className={cn("flex basis-full items-center justify-between gap-2", className)}
+      {...props}
+    />
+  );
+}
+
+function ItemFooter({ className, ...props }: React.ComponentProps<"div">) {
+  return (
+    <div
+      data-slot="item-footer"
+      className={cn("flex basis-full items-center justify-between gap-2", className)}
+      {...props}
+    />
+  );
+}
+
+export {
+  Item,
+  ItemMedia,
+  ItemContent,
+  ItemActions,
+  ItemGroup,
+  ItemSeparator,
+  ItemTitle,
+  ItemDescription,
+  ItemHeader,
+  ItemFooter,
+};