Fix sync_artwork clobbering is_primary via duplicate list entries

TMDb's images.posters/backdrops alternates commonly include the *same*
image as the top-level poster_path/backdrop_path -- so normalize_movie
legitimately produces the same provider_asset_id twice in one
artwork_list: once from the top-level field (is_primary=True), once
from the general alternates loop (is_primary=False, the default).
sync_artwork matched both occurrences to the same existing DB row by
provider_asset_id and did a plain overwrite each time, so whichever
occurrence it processed last won -- the non-primary duplicate always
came second in list order, so it silently un-set is_primary right
after the first occurrence had just set it.

Caught by re-ingesting The Matrix on a devbox with the artwork
download feature live: the movie ingested successfully, but zero
download jobs were ever enqueued because get_primary_artwork_ids
found nothing marked is_primary -- the flag had been clobbered back to
false immediately after being set.

Fixed by resetting is_primary on all existing rows up front (so a
provider dropping its "primary" pick on an image actually clears, not
just adds) and accumulating with OR within the batch instead of a
plain overwrite, so any primary occurrence in one sync sticks
regardless of processing order. Also dedupes brand-new rows within the
same batch the same way, closing the equivalent bug for images that
don't have an existing row yet.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

app/repositories/polymorphic.py

@@ -120,44 +120,57 @@ async def sync_artwork(
         .scalars()
         .all()
     )
-    existing_by_asset_id = {
+    by_asset_id: dict[str, Artwork] = {
         row.provider_asset_id: row for row in existing if row.provider_asset_id is not None
     }
+    # The incoming batch is authoritative for which image(s) are primary
+    # this sync — reset up front so a provider dropping its "primary" pick
+    # on an existing image actually clears here, not just adds.
+    for row in existing:
+        row.is_primary = False
 
     seen_asset_ids: set[str] = set()
     for art in artwork_list:
         art_type = art.artwork_type if art.artwork_type in _VALID_ARTWORK_TYPES else "poster"
-        matched = (
-            existing_by_asset_id.get(art.provider_asset_id) if art.provider_asset_id else None
-        )
+        asset_id = art.provider_asset_id
+        matched = by_asset_id.get(asset_id) if asset_id else None
         if matched is not None:
-            seen_asset_ids.add(art.provider_asset_id)  # type: ignore[arg-type]
             matched.artwork_type = ArtworkType(art_type)
             matched.width = art.width
             matched.height = art.height
             matched.aspect_ratio = art.aspect_ratio
             matched.vote_average = art.vote_average
-            matched.is_primary = art.is_primary
+            # OR, never a plain overwrite: the *same* image commonly
+            # appears twice in one provider fetch (TMDb's selected
+            # poster_path also shows up in the general posters alternates
+            # list) — once any occurrence in this batch says "primary",
+            # a later, non-primary occurrence of that same image must not
+            # un-set it.
+            matched.is_primary = matched.is_primary or art.is_primary
             matched.original_url = art.url
             # local_path/checksum deliberately untouched — see docstring.
         else:
-            session.add(
-                Artwork(
-                    entity_type=entity_type,
-                    entity_id=entity_id,
-                    artwork_type=ArtworkType(art_type),
-                    width=art.width,
-                    height=art.height,
-                    aspect_ratio=art.aspect_ratio,
-                    provider_id=provider_id,
-                    provider_asset_id=art.provider_asset_id,
-                    original_url=art.url,
-                    vote_average=art.vote_average,
-                    is_primary=art.is_primary,
-                )
+            new_row = Artwork(
+                entity_type=entity_type,
+                entity_id=entity_id,
+                artwork_type=ArtworkType(art_type),
+                width=art.width,
+                height=art.height,
+                aspect_ratio=art.aspect_ratio,
+                provider_id=provider_id,
+                provider_asset_id=asset_id,
+                original_url=art.url,
+                vote_average=art.vote_average,
+                is_primary=art.is_primary,
             )
-            if art.provider_asset_id:
-                seen_asset_ids.add(art.provider_asset_id)
+            session.add(new_row)
+            if asset_id:
+                # Register immediately so a second occurrence of this same
+                # new asset_id later in the batch updates this row instead
+                # of inserting a duplicate.
+                by_asset_id[asset_id] = new_row
+        if asset_id:
+            seen_asset_ids.add(asset_id)
 
     for row in existing:
         if row.provider_asset_id not in seen_asset_ids: