fix(pack): /pack/info reads ItemId via shadow FK, not nav property

PackController.Info's ownedItemsByItemId projection used `i.Item.Id` to
key the dict — EF translates that to the FK column today, but any future
model change that breaks the nav→column mapping would fall back to client
eval and collapse every key to 0 (the default Item constructor's Id),
silently hiding every tutorial pack via item_number=0. EF.Property<int>
reads the shadow FK directly and is robust to nav changes.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.EmulatedEntrypoint/Controllers/PackController.cs

@@ -63,10 +63,18 @@ public class PackController : SVSimController
         // OwnedItemEntry is [Owned] by Viewer, and EF refuses to track owned entities without
         // their owner in the result. Project to primitive pairs in the database query before
         // materialising into the dictionary — no entity tracking, single round-trip.
+        //
+        // Use EF.Property<int>(i, "ItemId") to read the shadow FK directly instead of going
+        // through the OwnedItemEntry.Item nav. The nav route works today (EF translates
+        // `i.Item.Id` to the FK column), but a future model change that renames the FK or
+        // breaks the nav→column mapping would silently fall back to client eval — where
+        // `i.Item.Id` returns 0 for every row (the default-initialised ItemEntry) and the
+        // dictionary collapses every ticket to item_number=0. Shadow-FK access bypasses
+        // that hazard entirely.
         var ownedItemsByItemId = await _db.Viewers
             .Where(v => v.Id == viewerId)
             .SelectMany(v => v.Items)
-            .Select(i => new { ItemId = (long)i.Item.Id, i.Count })
+            .Select(i => new { ItemId = (long)EF.Property<int>(i, "ItemId"), i.Count })
             .ToDictionaryAsync(x => x.ItemId, x => x.Count);
 
         return new PackInfoResponse