Todo repository protocol (#8)

This PR contains the work done to decouple the direct use of the `ModelContext` from `SwiftData` from the view model that uses it. In addition, the project transitioned to use Swift 6 and strict concurrency which brought some issues with the unit tests, so they were amended as well.

Reviewed-on: rock-n-code/todos-app#8
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

App/Sources/View Models/TaskListViewModel.swift

@@ -87,21 +87,21 @@ extension TaskListView {
 
         /// Deletes tasks at the specified indices.
         ///
-        /// This method removes tasks from the model context after a swipe-to-delete action.
-        /// The deletion is performed through SwiftData's model context, which handles
+        /// This method removes tasks from the repository after a swipe-to-delete action.
+        /// The deletion is performed through the repository, which handles
         /// persistence and triggers automatic UI updates.
         ///
         /// - Parameters:
         ///   - tasks: The current array of tasks.
         ///   - offsets: The index set of tasks to delete.
-        ///   - modelContext: The SwiftData model context to perform the deletion.
-        func deleteTasks(
+        ///   - repository: The repository to perform the deletion.
+        func delete(
             _ tasks: [Todo],
             at offsets: IndexSet,
-            from modelContext: ModelContext
+            from repository: TodoRepository
         ) {
             for index in offsets {
-                modelContext.delete(tasks[index])
+                repository.delete(tasks[index])
             }
         }