refactor: remove redundant networking task registry

[marinofaggiana]

Summary

• Replace the global NetworkingTasks registry with locally owned URLSessionTask references where cancellation and duplicate-request prevention are required.
• Keep request cancellation scoped to the view controller that started the request.
• Remove redundant task tracking from networking operations that never consumed the registered tasks.
• Remove the unused NetworkingTasks actor, its logging tag, and its Xcode project references.

Motivation

NetworkingTasks registered requests globally, but most registered tasks were never queried or cancelled. In addition, replacing an existing task could remove it from the registry without cancelling it, making later cancellation unreliable.

Keeping cancellable requests close to their owner makes their lifecycle explicit and avoids collisions between screens, accounts, or scenes using shared string identifiers.

Testing

Not run locally, following the repository guidance. Xcode build and test verification should be performed manually or by CI.

• The content of this PR was partly or fully generated using AI (N/A)