feat(db): properties_contents.placed_by, the character who placed a model

NULL is the owner (every model placed before this, and dashboard imports).
Read by GetPropertyModels and GetModel, written by InsertNewPropertyModel on
MySQL and SQLite, with a parity test.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

dDatabase/GameDatabase/ITables/IPropertyContents.h

@@ -18,6 +18,8 @@ public:
 		LOT lot{};
 		LWOOBJID ugcId{};
 		std::array<LWOOBJID, 5> behaviors{};
+		// The character who placed the model; 0 (NULL in the database) for the property's owner and older models
+		LWOOBJID placedBy{};
 	};
 
 	// Inserts a new UGC model into the database.