Prefer cached stills and stream first frames in the grid

poc/src/webui.ts

@@ -789,9 +789,20 @@ export function startWebUi(deps: WebUiDeps): WebUiHandle {
                 return;
             }
 
-            const upstream = await fetch(source.url, {
-                headers: req.headers.range ? { range: String(req.headers.range) } : {}
-            });
+            const rangeHeaders: Record<string, string> = req.headers.range
+                ? { range: String(req.headers.range) }
+                : {};
+            let upstream = await fetch(source.url, { headers: rangeHeaders });
+
+            // The signed CDN URL may have expired; re-fetch the message once and retry.
+            if (!upstream.ok && [403, 404, 410].includes(upstream.status)) {
+                const refreshed = await deps.media.refreshMediaUrl(
+                    String(req.params.scrapeId),
+                    Number(req.params.itemId)
+                );
+                if (refreshed) upstream = await fetch(refreshed, { headers: rangeHeaders });
+            }
+
             if (!upstream.ok && upstream.status !== 206) {
                 throw new HttpError(502, `upstream ${upstream.status}`);
             }