fix: address the 15 CodeRabbit findings from the wire-audit review

Security:
- roomcode PUT now requires instance ownership (any player could plant
  or relocate codes on foreign private instances)
- /platformid/{accountId} requires auth (anonymous Steam/Oculus id
  enumeration oracle)
- request tracing no longer captures successful /thread bodies by
  default (chat messages landed unredacted in logs); opt in via
  Trace__SuccessBodyPaths
- anonymous action-link renewal clamped to 720h per consume

Data integrity:
- buyPurchaseReminder upserts its objective sentinel (second purchase
  threw UNIQUE after the wallet was debited)
- progression reward gift + idempotency sentinel commit in one
  transaction (crash between them double-minted the reward)
- ClubPermissionsGalleryAndModeration migration defaults corrected to
  the entity contract (CommentsJson '[]', ClubChatEnabled true); new
  one-shot ClubChatDefaultRepair migration fixes databases that
  applied the wrong defaults; bootstrap repairs '' CommentsJson rows
- admin subroom-maxplayers audit entry commits with the mutation
- account purge covers CustomAvatarItems (ownership deleted, created
  items reassigned to the system account)
- duplicate photo reports ignored while one is unresolved

Stability:
- bootstrap only swallows the expected duplicate-column error; locked
  databases and schema failures now fail startup instead of the first
  endpoint
- clone blob write failure degrades to an empty sub-room instead of a
  500 after the clone row committed
- resumed photo-feed cursor stamped DateTimeKind.Utc (Npgsql rejects
  Unspecified for timestamptz)
- unreadcounts queries per requested room instead of materialising the
  whole comment keyspace

Tests:
- destroys-the-probe-session template guard is case-insensitive

74/74 tests pass.

DorkNet.Server/Services/PlayerAccountPurge.cs

@@ -144,6 +144,19 @@ public static class PlayerAccountPurge
                 .SetProperty(x => x.DeletedAt, now)
                 .SetProperty(x => x.IsPublic, false));
 
+        // Custom avatar items: the purged player's ownership rows go away;
+        // items they CREATED are reassigned to the system account like
+        // Inventions, because other players may own and be wearing them —
+        // deleting the item would break those avatars.
+        deleted += await db.CustomAvatarItemOwnership
+            .Where(x => x.PlayerId == playerId)
+            .ExecuteDeleteAsync();
+        reassigned += await db.CustomAvatarItems
+            .Where(x => x.CreatorPlayerId == playerId)
+            .ExecuteUpdateAsync(s => s
+                .SetProperty(x => x.CreatorPlayerId, systemPlayerId)
+                .SetProperty(x => x.UpdatedAt, now));
+
         reassigned += await db.SignupCodes
             .Where(x => x.RedeemedByPlayerId == playerId)
             .ExecuteUpdateAsync(s => s.SetProperty(x => x.RedeemedByPlayerId, (long?)null));