fix(mobile): show Refresh thumbnail only when preview missing or broken

The Refresh thumbnail button appeared on every scene, which is noise for the majority
that already have a good preview (report 26c114ed). Show it only when no source has a
usable thumbnail or the only thumbnails are rotting (sxyprn/trafficdeposit), which is
exactly when a manual refresh helps (the original d3376a71 case).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

mobile/src/screens/SceneDetailScreen.tsx

@@ -238,7 +238,16 @@ export function SceneDetailScreen() {
       <Hero data={data} />
 
       <View style={styles.body}>
-        {data.playback_sources.some((s) => s.origin?.startsWith('tube:')) && (
+        {/* Refresh tylko gdy BRAK dobrej miniatury (brak w ogóle lub rotting sxyprn/
+            trafficdeposit) — feedback 26c114ed: na scenach z dobrą miniaturą przycisk
+            był zbędnym szumem. Dla zepsutych/stałych nadal się pojawia (cel d3376a71). */}
+        {(() => {
+          const hasTube = data.playback_sources.some((s) => s.origin?.startsWith('tube:'));
+          const hasGoodThumb = data.playback_sources.some(
+            (s) => s.thumbnail_url && !/trafficdeposit|sxyprn|\/proxy\/sxyprn-thumb/i.test(s.thumbnail_url),
+          );
+          if (!hasTube || hasGoodThumb) return null;
+          return (
             <Pressable
               style={styles.refreshThumbBtn}
               onPress={() => refreshThumbMutation.mutate()}
@@ -248,7 +257,8 @@ export function SceneDetailScreen() {
                 {refreshThumbMutation.isPending ? 'Refreshing thumbnail…' : '↻ Refresh thumbnail'}
               </Text>
             </Pressable>
-        )}
+          );
+        })()}
 
         {(data.code || data.director) && (
           <View style={styles.metaRow}>