Fix thumbnail loading and startup gallery refresh.

Refresh gallery metadata after thumbnail generation so new thumb URLs are available immediately, and lazy-load gallery thumbnails with IntersectionObserver to avoid fetching all images on initial page load.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/templates/gallery.templ

@@ -22,7 +22,9 @@ templ GalleryGrid(images []gallery.Image) {
 			>
 				if img.ThumbURL != "" {
 					<img
-						src={ img.ThumbURL }
+						src="data:image/gif;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs="
+						data-src={ img.ThumbURL }
+						class="lazy-thumb"
 						alt={ fmt.Sprintf("%s — %s", gallery.AlbumLabel(img.Album), formatDate(img.Date)) }
 						loading="lazy"
 						decoding="async"

app/templates/layout.templ

@@ -34,6 +34,47 @@ templ Layout(title string, preloadImage string, content templ.Component) {
 			</footer>
 			<div id="modal-root"></div>
 			<script src="/static/htmx.min.js" defer></script>
+			<script>
+				(function () {
+					function hydrateLazyThumbs(root) {
+						var lazyImages = root.querySelectorAll("img[data-src]");
+						if (!lazyImages.length) return;
+
+						if (!("IntersectionObserver" in window)) {
+							lazyImages.forEach(function (img) {
+								img.src = img.dataset.src;
+								img.removeAttribute("data-src");
+							});
+							return;
+						}
+
+						var observer = new IntersectionObserver(
+							function (entries) {
+								entries.forEach(function (entry) {
+									if (!entry.isIntersecting) return;
+									var img = entry.target;
+									img.src = img.dataset.src;
+									img.removeAttribute("data-src");
+									observer.unobserve(img);
+								});
+							},
+							{ rootMargin: "300px 0px" },
+						);
+
+						lazyImages.forEach(function (img) {
+							observer.observe(img);
+						});
+					}
+
+					document.addEventListener("DOMContentLoaded", function () {
+						hydrateLazyThumbs(document);
+					});
+
+					document.body.addEventListener("htmx:afterSwap", function (event) {
+						hydrateLazyThumbs(event.target);
+					});
+				})();
+			</script>
 		</body>
 	</html>
 }