Application: list containers & blobs with pagination

Goal

Implement the core "browse" use cases: list containers in an account, and list blobs in a container.

Why

G2 reviews call out Storage Explorer's slow performance on large data sets; loading everything into memory at once is a big part of that. Building pagination in from the start avoids repeating that mistake.

Tasks

• Add IBlobContainerRepository/IBlobRepository ports (or similar names) in AzStorage.Application with paged listing methods (page size + continuation token in, page of results + next token out).
• Add ListContainersUseCase and ListBlobsUseCase (support an optional folder-prefix parameter to browse virtual folders).
• Implement the ports in AzStorage.Infrastructure using BlobServiceClient/BlobContainerClient's built-in paged (AsPages) APIs.
• Add unit tests (fake repository) for the use cases and integration tests (Azurite) for the real implementation, including a case with more items than a single page.

Acceptance Criteria

• Listing 1 page of containers/blobs does not require fetching the entire container/account contents.
• Continuation-token-based paging is covered by at least one integration test with 2+ pages.

Depends on

• Domain: model Blob Container and Blob Item
• Infrastructure: implement Azure Blob Storage adapter

Start in AzStorage.Application by defining the repository ports and list use cases, then inspect AzStorage.Infrastructure for the Azure Blob Storage adapter using BlobServiceClient and BlobContainerClient.AsPages. Add fake-repository unit tests and Azurite integration tests, including more items than one page. Done means continuation-token paging and optional folder prefixes work without fetching all contents.