refactor: Upload backend router

[PhilippeWeidmann]

This pull request introduces a new abstraction, UploadBackendRouter, to centralize and streamline upload session management and URL creation, especially in preparation for supporting multiple API versions and user types. The changes refactor upload-related flows to use this new router, update UI state initialization, and improve transfer URL handling for both v1 and v2 APIs.

[Copilot]

Pull request overview

This PR introduces UploadBackendRouter as a central abstraction for upload session handling, and refactors upload-related UI + worker flows to use it in preparation for multiple backends/API versions.

Changes:

• Added UploadBackendRouter and wired it into MainViewState initialization paths (preloading/onboarding).
• Refactored upload progress + background continuation flow to pass the router through to TransferManagerWorker.
• Simplified local upload session creation by returning the local session UUID instead of a SendableUploadSession.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
SwissTransferFeatures/UploadProgressView/UploadProgress/UploadProgressView.swift	Switches upload initialization/restoration to use UploadBackendRouter.
SwissTransferFeatures/UploadProgressView/UploadError/UploadErrorView.swift	Updates retry flow to transition using a local session UUID.
SwissTransferFeatures/UploadProgressView/UploadContinuationCoordinator.swift	Passes UploadBackendRouter through background/foreground upload continuation paths.
SwissTransferFeatures/UploadProgressView/TransferSessionManager.swift	Updates worker creation and upload entrypoint to use the router.
SwissTransferFeatures/PreloadingView/PreloadingView.swift	Creates/injects UploadBackendRouter into MainViewState during startup routing.
SwissTransferFeatures/OnboardingView/OnboardingView.swift	Creates/injects UploadBackendRouter when entering main view from onboarding deep links.
SwissTransferFeatures/OnboardingView/OnboardingBottomButtonsView.swift	Creates/injects UploadBackendRouter when opening a guest session.
SwissTransferFeatures/NewTransferView/VerifyMailView.swift	Updates email verification flow to transition using a local session UUID.
SwissTransferFeatures/NewTransferView/NewTransferView.swift	Uses router to create local upload session UUID; updates share extension import URL creation.
SwissTransferCore/UploadManager+Extension.swift	Renames API to return local upload session UUID instead of wrapping in SendableUploadSession.
SwissTransferCore/Upload/UploadBackendRouter.swift	Adds the new router abstraction (currently partially implemented).
SwissTransferCore/Upload/TransferManagerWorker.swift	Replaces uploadManager dependency with UploadBackendRouter and routes finish through it.
SwissTransferCore/Upload/TransferManagerWorker+Network.swift	Uses router (currently via its underlying sharedApiUrlCreator) to build chunk upload URLs.

Comments suppressed due to low confidence (1)

SwissTransferCore/Upload/TransferManagerWorker+Network.swift:33

• TransferManagerWorker builds the chunk upload URL by reaching through uploadBackendRouter.swissTransferManager.sharedApiUrlCreator, which bypasses the new router abstraction and makes it harder to support multiple backends/API versions. Expose a dedicated URL-building method on UploadBackendRouter (e.g. uploadChunkURL(...)) and keep swissTransferManager encapsulated so the worker doesn’t need to know which API creator to use.

        guard let rawChunkURL = try uploadBackendRouter.swissTransferManager.sharedApiUrlCreator.uploadChunkUrl(
            uploadUUID: chunk.uploadUUID,
            fileUUID: chunk.remoteUploadFileUUID,
            chunkIndex: Int32(chunk.index),
            isLastChunk: chunk.isLast,
            isRetry: false
        ) else {

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud