fix(preview): show image preview instead of 'Conversion complete' for blob URLs

canBrowserPreview() was checking for a file extension in blob: URLs, which
have none (blob:http://localhost:1349/<uuid>). This caused the optimize-for-web
live preview — which stores a blob: URL in processedUrl — to always return false
and show the 'Conversion complete' fallback card instead of the BeforeAfterSlider.

Fix: blob: URLs are always renderable in <img> tags; short-circuit the extension
check with `if (url.startsWith('blob:')) return true` in both tool-page.tsx and
multi-image-viewer.tsx.

apps/web/src/components/common/multi-image-viewer.tsx

@@ -18,6 +18,7 @@ const BROWSER_PREVIEWABLE_EXTS = new Set([
 ]);
 
 function canBrowserPreview(url: string): boolean {
+  if (url.startsWith("blob:")) return true;
   const ext = decodeURIComponent(url).split(".").pop()?.toLowerCase() ?? "";
   return BROWSER_PREVIEWABLE_EXTS.has(ext);
 }

apps/web/src/pages/tool-page.tsx

@@ -41,7 +41,9 @@ const BROWSER_PREVIEWABLE_EXTS = new Set([
 ]);
 
 function canBrowserPreview(url: string, filename?: string | null): boolean {
-  // For blob URLs from batch processing, check the real filename instead
+  // Blob URLs are always renderable in <img> tags — no extension to check
+  if (url.startsWith("blob:")) return true;
+  // For batch results, check the stored filename (has extension) rather than the blob URL
   const source = filename ?? url;
   const ext = decodeURIComponent(source).split(".").pop()?.toLowerCase() ?? "";
   return BROWSER_PREVIEWABLE_EXTS.has(ext);