Web support for the Website service (#17)

This PR contains the work done to introduce a new Web Swift package that provides a reusable, declarative way to register route controllers on a Hummingbird router, then adopt it in the Website service.

To provide further details about the work:

* Web package
  * The `RouterController` protocol — a Sendable protocol to group controllers behind one `routes` property.
  * The `RouteCollectionBuilder`  — a result builder that collects controllers' route collections into a stack, with full support for optionals, conditionals, and arrays.
  * The `addController(_:)` method — a `RouterMethods` extension letting controllers be listed declaratively and adding each one's routes at the router root.

* Website service
  * Added Web as a dependency of the _WebsiteLibrary_ target.
  * Conformed the `RootController` and `HealthController`controllers to the `RouterController` protocol.
  * Updated the `App+Build` extension to to use the cleaner `router.addController { … }` instead.

Reviewed-on: rock-n-code/loud-amsterdam#17
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Services/Website/Sources/App/Extensions/App+Build.swift

@@ -157,9 +157,11 @@ private func router(
         )
     }
 
-    router.addRoutes {
-        RootController<AppRequestContext>().routes
-        HealthController<AppRequestContext>(probe: probe).routes
+    router.addController {
+        RootController<AppRequestContext>()
+        HealthController<AppRequestContext>(
+            probe: probe
+        )
     }
 
     return router