domain: primaryImageTag -> imageId end-to-end (phase 4a/4b)

Rust: PlayerMediaItem and MergedMediaItem gain image_id (dual-carry),
populated from primary_image_tag at every construction/conversion site.
Regenerated bindings.

Frontend: all catalog + player + merged readers now use imageId. The
NowPlayingItem->MediaItem bridge (player.ts) properly maps the remote
session's Jellyfin fields (Type, runTimeTicks, primaryImageTag) onto the
neutral kind/durationMs/imageId. Types that are genuinely out of scope
(Person, NowPlayingItem, PlayItemRequest) keep primaryImageTag.

Rust 456, frontend 644, check clean.

src/lib/components/library/ArtistDetailView.svelte

@@ -112,12 +112,12 @@
     <!-- Artist Info -->
     <div class="flex flex-col items-center text-center py-12">
       <!-- Artist Image -->
-      {#if artist.primaryImageTag}
+      {#if artist.imageId}
         <div class="mb-6 rounded-full overflow-hidden w-40 h-40 shadow-lg">
           <CachedImage
             itemId={artist.id}
             imageType="Primary"
-            tag={artist.primaryImageTag}
+            tag={artist.imageId}
             maxWidth={400}
             alt={artist.name}
             class="w-full h-full object-cover"
@@ -160,11 +160,11 @@
             class="group cursor-pointer"
           >
             <div class="aspect-square bg-[var(--color-surface)] rounded-lg overflow-hidden mb-2 group-hover:opacity-80 transition-opacity">
-              {#if album.primaryImageTag}
+              {#if album.imageId}
                 <CachedImage
                   itemId={album.id}
                   imageType="Primary"
-                  tag={album.primaryImageTag}
+                  tag={album.imageId}
                   maxWidth={200}
                   alt={album.name}
                   class="w-full h-full object-cover"
@@ -218,11 +218,11 @@
               class="group text-center"
             >
               <div class="w-32 h-32 bg-[var(--color-surface)] rounded-full overflow-hidden mb-2 mx-auto group-hover:opacity-80 transition-opacity">
-                {#if relatedArtist.primaryImageTag}
+                {#if relatedArtist.imageId}
                   <CachedImage
                     itemId={relatedArtist.id}
                     imageType="Primary"
-                    tag={relatedArtist.primaryImageTag}
+                    tag={relatedArtist.imageId}
                     maxWidth={200}
                     alt={relatedArtist.name}
                     class="w-full h-full object-cover"

src/lib/components/library/EpisodeFocusView.svelte

@@ -77,8 +77,8 @@
     if (episode.backdropImageTags?.[0]) {
       return { itemId: episode.id, imageType: "Backdrop" as const, tag: episode.backdropImageTags[0] };
     }
-    if (episode.primaryImageTag) {
-      return { itemId: episode.id, imageType: "Primary" as const, tag: episode.primaryImageTag };
+    if (episode.imageId) {
+      return { itemId: episode.id, imageType: "Primary" as const, tag: episode.imageId };
     }
     if (series.backdropImageTags?.[0]) {
       return { itemId: series.id, imageType: "Backdrop" as const, tag: series.backdropImageTags[0] };
@@ -246,7 +246,7 @@
             <CachedImage
               itemId={ep.id}
               imageType="Primary"
-              tag={ep.primaryImageTag}
+              tag={ep.imageId}
               maxWidth={400}
               alt={ep.name}
               class="w-full h-full object-cover transition-transform {isCurrent ? '' : 'group-hover/card:scale-105'}"

src/lib/components/library/EpisodeRow.svelte

@@ -59,7 +59,7 @@
     <CachedImage
       itemId={episode.id}
       imageType="Primary"
-      tag={episode.primaryImageTag}
+      tag={episode.imageId}
       maxWidth={320}
       alt={episode.name}
       class="w-full h-full object-cover transition-transform group-hover/row:scale-105"

src/lib/components/library/GenericGenreBrowser.svelte

@@ -234,7 +234,7 @@
                 <CachedImage
                   itemId={item.id}
                   imageType="Primary"
-                  tag={item.primaryImageTag}
+                  tag={item.imageId}
                   maxWidth={300}
                   alt={item.name}
                   class="w-full h-full object-cover group-hover:scale-105 transition-transform"

src/lib/components/library/LibraryListView.svelte

@@ -19,7 +19,7 @@
   }
 
   function getImageTag(item: MediaItem | Library): string | undefined {
-    return "primaryImageTag" in item ? (item.primaryImageTag ?? undefined) : ("imageTag" in item ? (item.imageTag ?? undefined) : undefined);
+    return "imageId" in item ? (item.imageId ?? undefined) : ("imageTag" in item ? (item.imageTag ?? undefined) : undefined);
   }
 
   function getSubtitle(item: MediaItem | Library): string {

src/lib/components/library/MediaCard.svelte

@@ -113,7 +113,7 @@
   });
 
   const imageTag = $derived(
-    "primaryImageTag" in item ? item.primaryImageTag : ("imageTag" in item ? item.imageTag : undefined)
+    "imageId" in item ? item.imageId : ("imageTag" in item ? item.imageTag : undefined)
   );
 
   const maxWidth = $derived(size === "large" ? 400 : size === "medium" ? 300 : 200);

src/lib/components/library/PersonDetailView.svelte

@@ -53,7 +53,7 @@
       <CachedImage
         itemId={person.id}
         imageType="Primary"
-        tag={person.primaryImageTag}
+        tag={person.imageId}
         maxWidth={400}
         alt={person.name}
         class="w-full rounded-lg shadow-lg"

src/lib/components/library/PlaylistDetailView.svelte

@@ -146,11 +146,11 @@
   <div class="flex gap-6 pt-4">
     <!-- Playlist artwork -->
     <div class="flex-shrink-0 w-48">
-      {#if playlist.primaryImageTag}
+      {#if playlist.imageId}
         <CachedImage
           itemId={playlist.id}
           imageType="Primary"
-          tag={playlist.primaryImageTag}
+          tag={playlist.imageId}
           maxWidth={400}
           alt={playlist.name}
           class="w-full rounded-lg shadow-lg"

src/lib/components/library/SeasonSection.svelte

@@ -28,7 +28,7 @@
       <CachedImage
         itemId={season.id}
         imageType="Primary"
-        tag={season.primaryImageTag}
+        tag={season.imageId}
         maxWidth={200}
         alt={seasonName}
         class="w-full h-full object-cover"