feat: propagate OBJECT_FIELD_SCALE_X through creature and GO spawn pipeline

Reads OBJECT_FIELD_SCALE_X (field 4, cross-expansion) from CREATE_OBJECT
update fields and passes it through the full creature and game object spawn
chain: game_handler callbacks → pending spawn structs → async load results
→ createInstance() calls. This gives boss giants, gnomes, children, and
other non-unit-scale NPCs correct visual size, and ensures scaled GOs
(e.g. large treasure chests, oversized plants) render at the server-specified
scale rather than always at 1.0.

- Added OBJECT_FIELD_SCALE_X to UF enum and all expansion update_fields.json
- Added float scale to CreatureSpawnCallback and GameObjectSpawnCallback
- Propagated scale through PendingCreatureSpawn, PreparedCreatureModel,
  PendingGameObjectSpawn, PreparedGameObjectWMO
- Used scale in charRenderer/m2Renderer/wmoRenderer createInstance() calls
- Sanity-clamped raw float to [0.01, 100.0] range before use

include/game/update_field_table.hpp

@@ -14,6 +14,7 @@ namespace game {
 enum class UF : uint16_t {
     // Object fields
     OBJECT_FIELD_ENTRY,
+    OBJECT_FIELD_SCALE_X,
 
     // Unit fields
     UNIT_FIELD_TARGET_LO,