fix(ui): a picture that fails to load shows the card's own frame, then retries

A bare <img> sent a Referer that Google's image CDNs refuse and had no retry and no fallback, so a
Home shelf card showed the browser's broken-image mark. ui/RemoteImage gathers what Avatar, the
channel banner and the download rows had each hand-rolled: no Referer, up to three retries past the
browser's negative cache, the caller's fallback (by default the card's empty frame) instead of the
broken mark, the failure remembered by URL. Every picture now goes through it; a lint rule refuses
a bare <img>.

frontend/src/components/plexDetailUi.tsx

@@ -16,6 +16,7 @@ import { Pressable } from "./ui/Pressable";
 import { SURFACE } from "./ui/surfaces";
 import { Badge } from "./ui/Badge";
 import { Chip } from "./ui/Chip";
+import RemoteImage from "./ui/RemoteImage";
 
 // Shared "detail page" UI reused by the movie info page (PlexInfo) and the series show/season pages,
 // so they look consistent (the standing glassy/HTPC brief): the faint fixed art backdrop, the two
@@ -263,10 +264,13 @@ export function DetailHero({
         className={`group/poster relative ${posterSizeClass} shrink-0 self-start`}
         title={posterTitle}
       >
-        <img
+        <RemoteImage
           src={thumb}
           alt=""
           className="w-full aspect-2/3 object-cover rounded-xl border border-border"
+          fallback={
+            <div className="w-full aspect-2/3 rounded-xl border border-border bg-surface" />
+          }
         />
         {showPlayOverlay && (
           <div className="absolute inset-0 rounded-xl bg-black/40 opacity-0 group-hover/poster:opacity-100 transition grid place-items-center">