Warn on small picture candidates

public/app.ts

@@ -61,6 +61,7 @@ const darkContrastSelect = document.querySelector("#darkContrastSelect");
 const catalogScreen = document.querySelector(".catalog-screen");
 const secondaryPanelToggle = document.querySelector("#secondaryPanelToggle");
 const mainWorkspaceToggle = document.querySelector("#mainWorkspaceToggle");
+const MIN_PRODUCT_PICTURE_SIZE = 800;
 let sidebarUserClosed = false;
 let mappingLoadToken = 0;
 const mappingCacheKey = "catalog-maker:mapping-cache";
@@ -985,12 +986,21 @@ function renderPictureCandidates(items) {
         dimensions.className = "picture-candidate-dimensions";
         dimensions.textContent = "Size: loading...";
         image.addEventListener("load", () => {
-          dimensions.textContent = image.naturalWidth && image.naturalHeight
-            ? `Size: ${image.naturalWidth} x ${image.naturalHeight}px`
-            : "Size: unknown";
+          if (!image.naturalWidth || !image.naturalHeight) {
+            dimensions.textContent = "Size: unknown";
+            row.classList.remove("is-too-small");
+            return;
+          }
+
+          const isTooSmall = image.naturalWidth < MIN_PRODUCT_PICTURE_SIZE || image.naturalHeight < MIN_PRODUCT_PICTURE_SIZE;
+          row.classList.toggle("is-too-small", isTooSmall);
+          dimensions.textContent = isTooSmall
+            ? `Size: ${image.naturalWidth} x ${image.naturalHeight}px - too small, min ${MIN_PRODUCT_PICTURE_SIZE} x ${MIN_PRODUCT_PICTURE_SIZE}`
+            : `Size: ${image.naturalWidth} x ${image.naturalHeight}px`;
         });
         image.addEventListener("error", () => {
           dimensions.textContent = "Size: image preview failed";
+          row.classList.add("is-too-small");
         });
 
         const assignment = document.createElement("span");