Add Repository Query Command

Repository Query and Command implementation details

• Add repository types in the BlazorApp/Repositories folder.
• Keep read operations in BlazorApp/Repositories/<Feature>Query.cs and write operations in BlazorApp/Repositories/<Feature>Command.cs.
• Add methods to an existing repository pair when the data access belongs to the same feature; create a new query/command pair when introducing a new feature.
• Inject IDbContextFactory<TodoDbContext> into repository primary constructors.
• Create a fresh TodoDbContext inside each repository method with CreateDbContextAsync(cancellationToken).
• Use AsNoTracking() for query methods unless the method must intentionally return tracked entities from the same context.
• Keep filtering, ordering, includes, and projection in the query layer.
• Keep inserts, updates, and deletes in the command layer and call SaveChangesAsync(cancellationToken) after the mutation work is complete.
• For update and delete operations, load the current entity first and return a clear result such as when the target record does not exist.