[BR-2165]:feat/add multipart download for shared files

[jaaaaavier]

Description

Adds multipart download support to public shared file links.

Changes:

• NetworkFacade.downloadChunk: honor options?.key as an override for the SDK-derived decryption key, mirroring the existing behavior in download(). Needed because shared links have no mnemonic to derive a key from the real key is the link's own encryptionKey.
• download/v2.ts: split multipartDownload into multipartDownloadOwnFile (existing behavior) and a new multipartDownloadSharedFile, dispatching on token && encryptionKey, the same discriminator already used by downloadFile() for the non-multipart case.
• network/index.ts: re-export multipartDownloadFile from the network facade so it's actually reachable from views (it already existed in download.ts but wasn't exposed).
• ShareFileView.tsx: use network.multipartDownloadFile when fileInfo.item.size >= MIN_DOWNLOAD_MULTIPART_SIZE, otherwise keep the regular single-request downloadFile`.

Related Issues

Related Pull Requests

Checklist

• Changes have been tested locally.
• Unit tests have been written or updated as necessary.
• The code adheres to the repository's coding standards.
• Relevant documentation has been added or updated.
• No new warnings or errors have been introduced.
• SonarCloud issues have been reviewed and addressed.
• QA Passed

Testing Process

Manually verified in the browser: shared files above the threshold trigger multiple parallel 206 Partial Content range requests instead of one single request, and the resulting file downloads and decrypts correctly.

Additional Notes

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sg-gs]

Shouldn't this be called with the overrideKey?