feat: add pdf image renderer (#2554)

## Description

Replace the PDF renderer with an custom image renderer.

This allows us to remove the "react-pdf" dependency and allows us to use
a virtual list to improve performance.

apps/remix/app/components/general/pdf-viewer/use-scroll-to-page.ts

@@ -0,0 +1,46 @@
+import { type RefObject, useEffect } from 'react';
+
+/**
+ * Watch for `data-scroll-to-page` attribute changes on a container element.
+ *
+ * When set (by `validateFieldsInserted`, `handleOnNextFieldClick`, or similar),
+ * scroll the virtual list to the requested page and clear the attribute.
+ *
+ * This is the communication bridge between field validation logic (which knows
+ * which page to scroll to) and the virtual list (which knows how to scroll).
+ */
+export const useScrollToPage = (
+  contentRef: RefObject<HTMLElement | null>,
+  scrollToItem: (index: number) => void,
+) => {
+  useEffect(() => {
+    const el = contentRef.current;
+
+    if (!el) {
+      return;
+    }
+
+    const observer = new MutationObserver((mutations) => {
+      for (const mutation of mutations) {
+        if (mutation.type === 'attributes' && mutation.attributeName === 'data-scroll-to-page') {
+          const raw = el.getAttribute('data-scroll-to-page');
+
+          if (raw) {
+            const pageNumber = parseInt(raw, 10);
+
+            if (!isNaN(pageNumber) && pageNumber >= 1) {
+              // Pages are 1-indexed, virtual list items are 0-indexed.
+              scrollToItem(pageNumber - 1);
+            }
+
+            el.removeAttribute('data-scroll-to-page');
+          }
+        }
+      }
+    });
+
+    observer.observe(el, { attributes: true, attributeFilter: ['data-scroll-to-page'] });
+
+    return () => observer.disconnect();
+  }, [contentRef, scrollToItem]);
+};