feat: implement ImageLightbox with tests

src/shared/ui/ImageLightbox/ui/ImageLightbox.test.tsx

@@ -41,21 +41,22 @@ describe('ImageLightbox', () => {
 
     it('clicking the close button closes the dialog', () => {
       render(<ImageLightbox {...DEFAULT_PROPS} />);
-      fireEvent.click(screen.getByRole('button', { name: /close/i }));
+      fireEvent.click(screen.getByRole('button', { name: 'My Project' })); // open first
+      fireEvent.click(screen.getByRole('button', { name: /close/i, hidden: true }));
       expect(HTMLDialogElement.prototype.close).toHaveBeenCalledTimes(1);
     });
 
     it('clicking the backdrop (dialog element itself) closes the dialog', () => {
       render(<ImageLightbox {...DEFAULT_PROPS} />);
-      const dialog = document.querySelector('dialog')!;
+      const dialog = document.querySelector('dialog') as HTMLDialogElement;
       fireEvent.click(dialog, { target: dialog });
       expect(HTMLDialogElement.prototype.close).toHaveBeenCalledTimes(1);
     });
 
     it('clicking inside the dialog (not backdrop) does not close', () => {
       render(<ImageLightbox {...DEFAULT_PROPS} />);
-      const dialog = document.querySelector('dialog')!;
-      const inner = dialog.querySelector('div')!;
+      const dialog = document.querySelector('dialog') as HTMLDialogElement;
+      const inner = dialog.querySelector('div') as HTMLDivElement;
       fireEvent.click(inner);
       expect(HTMLDialogElement.prototype.close).not.toHaveBeenCalled();
     });

src/shared/ui/ImageLightbox/ui/ImageLightbox.tsx

@@ -1,5 +1,9 @@
 'use client';
 
+import Image from 'next/image';
+import { useRef } from 'react';
+import { cn } from '$shared/lib';
+
 type Props = {
   /**
    * Image source URL
@@ -18,6 +22,65 @@ type Props = {
 /**
  * Clickable image thumbnail that opens a fullscreen brutalist dialog on click.
  */
-export function ImageLightbox(_props: Props) {
-  return null;
+export function ImageLightbox({ src, alt, className }: Props) {
+  const dialogRef = useRef<HTMLDialogElement>(null);
+
+  function open() {
+    dialogRef.current?.showModal();
+  }
+
+  function close() {
+    dialogRef.current?.close();
+  }
+
+  function handleBackdropClick(e: React.MouseEvent<HTMLDialogElement>) {
+    if (e.target === e.currentTarget) {
+      close();
+    }
+  }
+
+  /**
+   * Keyboard equivalent of backdrop click — closes the dialog when the user
+   * activates the backdrop area (dialog element itself) via Enter or Space.
+   * ESC is handled natively by showModal(); this covers explicit backdrop activation.
+   */
+  function handleBackdropKeyUp(e: React.KeyboardEvent<HTMLDialogElement>) {
+    if (e.target === e.currentTarget && (e.key === 'Enter' || e.key === ' ')) {
+      close();
+    }
+  }
+
+  return (
+    <>
+      <button
+        type="button"
+        onClick={open}
+        aria-label={alt}
+        className={cn('relative block w-full aspect-video overflow-hidden cursor-zoom-in', className)}
+      >
+        <Image src={src} alt={alt} fill className="object-cover" />
+      </button>
+
+      <dialog
+        ref={dialogRef}
+        aria-label={alt}
+        onClick={handleBackdropClick}
+        onKeyUp={handleBackdropKeyUp}
+        className="lightbox bg-blue brutal-border shadow-brutal-xl p-0 max-w-5xl w-full"
+      >
+        <div className="relative aspect-video w-full">
+          {/* aria-hidden: the dialog element itself carries the accessible label */}
+          <Image src={src} alt={alt} fill className="object-contain" aria-hidden={true} />
+        </div>
+        <button
+          type="button"
+          onClick={close}
+          aria-label="Close image"
+          className="absolute top-3 right-3 bg-blue text-cream brutal-border px-3 py-1 text-sm font-bold"
+        >
+          Close
+        </button>
+      </dialog>
+    </>
+  );
 }