feat: branding furni image position + scale (MPU background editor)

Renderer support for the in-client image position editor:
- FurnitureBrandedImageVisualization applies offsetX/Y to the branded image
  layer only (offsetZ stays as z-index/depth), so the image can be moved
  without shifting the furni frame
- new `scale` branding key + FURNITURE_BRANDING_SCALE: zooms the image via a
  real per-sprite scale (RoomObjectSprite.scale, default 1, applied in
  RoomSpriteCanvas) — NOT by writing the read-only width/height
- AssetManager loads external raster images (png/jpg/…) via a CORS <img> +
  Texture.from instead of Assets.load (which didn't load cross-origin images);
  branding image download failures are now surfaced instead of swallowed

packages/api/src/nitro/room/object/RoomObjectVariable.ts

@@ -76,6 +76,7 @@ export class RoomObjectVariable
     public static FURNITURE_BRANDING_OFFSET_X: string = 'furniture_branding_offset_x';
     public static FURNITURE_BRANDING_OFFSET_Y: string = 'furniture_branding_offset_y';
     public static FURNITURE_BRANDING_OFFSET_Z: string = 'furniture_branding_offset_z';
+    public static FURNITURE_BRANDING_SCALE: string = 'furniture_branding_scale';
     public static FURNITURE_BADGE_IMAGE_STATUS: string = 'furniture_badge_image_status';
     public static FURNITURE_BADGE_ASSET_NAME: string = 'furniture_badge_asset_name';
     public static FURNITURE_BADGE_VISIBLE_IN_STATE: string = 'furniture_badge_visible_in_state';

packages/api/src/room/object/visualization/IRoomObjectSprite.ts

@@ -11,6 +11,7 @@ export interface IRoomObjectSprite
     texture: Texture;
     width: number;
     height: number;
+    scale: number;
     offsetX: number;
     offsetY: number;
     flipH: boolean;