Clean up Client ContainerSystem

[TheShuEd]

some minor refactor of client ContainerSystem:

• moved to file-scoped namespace
• Added SpriteSystem dependency and rewrite obsoleted code from

sprite.ContainerOccluded = spriteOccluded;

to

_sprite.SetContainerOccluded((entity, sprite), spriteOccluded);

• update EntityQuery initialization via dependency injection

    [Dependency] private EntityQuery<PointLightComponent> _pointLightQuery = default!;
    [Dependency] private EntityQuery<SpriteComponent> _spriteQuery = default!;

Zero logic changes