fix: move AlbHealthCheckLayer outside CoffeeShop to fix /ping routing

[PeterUlb]

Background

• The smithy-rust-quickstart template places the AlbHealthCheckLayer inside the CoffeeShopConfig builder. At that level, Smithy's router rejects /ping as an unknown operation and returns a 404. This PR moves the health check layer outside the CoffeeShop service so it intercepts requests before routing, and /ping correctly returns 200.
• No new example was added.

Testing

• Ran the quickstart server locally and confirmed /ping returns 200 instead of 404.
• No integration test was added.
• N/A - no new example was added.

Links

• N/A

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