Allow the user to forward the same message to multiple rooms at once

This will send the item to the rooms in order they were chosen and only deep link
into the target room if single, otherwise it will just dismiss the forwarding screen
after sending.

UnitTests/Sources/MessageForwardingScreenViewModelTests.swift

@@ -37,7 +37,7 @@ struct MessageForwardingScreenViewModelTests {
     @Test
     mutating func roomSelection() {
         context.send(viewAction: .selectRoom(roomID: "2"))
-        #expect(context.viewState.selectedRoomID == "2")
+        #expect(context.viewState.selectedRoomIDs == ["2"])
     }
     
     @Test
@@ -54,12 +54,12 @@ struct MessageForwardingScreenViewModelTests {
     @Test
     mutating func forwarding() async throws {
         context.send(viewAction: .selectRoom(roomID: "2"))
-        #expect(context.viewState.selectedRoomID == "2")
+        #expect(context.viewState.selectedRoomIDs == ["2"])
         
         let deferred = deferFulfillment(viewModel.actions) { action in
             switch action {
-            case .sent(let roomID):
-                return roomID == "2"
+            case .sent(let roomIDs):
+                return roomIDs == ["2"]
             default:
                 return false
             }