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>

Packages/Web/Package.swift

@@ -0,0 +1,47 @@
+// swift-tools-version: 6.3
+
+import PackageDescription
+
+let package = Package(
+    name: "Web",
+    platforms: [
+        .macOS(.v15),
+    ],
+    products: [
+        .library(
+            name: "Web",
+            targets: [
+                "Web"
+            ]
+        ),
+    ],
+    dependencies: [
+        .package(
+            url: "https://github.com/hummingbird-project/hummingbird.git",
+            from: "2.25.0"
+        ),
+    ],
+    targets: [
+        .target(
+            name: "Web",
+            dependencies: [
+                .product(
+                    name: "Hummingbird",
+                    package: "hummingbird"
+                ),
+            ],
+            path: "Sources"
+        ),
+        .testTarget(
+            name: "WebTests",
+            dependencies: [
+                .byName(name: "Web"),
+                .product(
+                    name: "HummingbirdTesting",
+                    package: "hummingbird"
+                ),
+            ],
+            path: "Tests"
+        ),
+    ]
+)