Function setupCaches

Build the L0/L1/L2 cache stack and return the raw store the caller should pass to the Luxar Zarr facade's openStore().

Behavior matches the previous inline block in SceneLoader.loadScene():

• L0 is enabled iff appConfig.cache.l0Enabled && !flags.noCache.
• L1/L2 are enabled iff appConfig.cache.enabled && !flags.noCache.
• When L1/L2 + L0 are both active, L0 is registered as an invalidation listener so a content-hash bump clears all three.
• When caching is fully disabled, falls back to a vanilla fetch store created by the Luxar Zarr facade.