fix(alldebrid): don't treat a ready magnet with no files yet as downloaded

[NoxzRCW]

📌 Description

• Fixes decypharr marking a torrent as downloaded with zero files when AllDebrid reports it ready before the files list is actually populated in that same response. This is the empty symlink folder people are hitting in Radarr not processing Decypharr symlinks #113 and Decypharr symlink issue on qbit mount #122.

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Target Branch Check (IMPORTANT)

• I confirm this PR is targeting the correct branch

Expected target:

• beta (for features)

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Changes Made

• Extracted the progress/files handling from GetTorrent and updateTorrent into a shared applyMagnetFiles helper
• When status is "downloaded" but the flattened files list is empty and the reported size is greater than zero, keep the torrent as downloading instead of downloaded
• Added tests covering both the empty files case and the normal case where files are present

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Testing

• Tested locally

Steps:

1. Wrote a fake /magnet/status server returning statusCode 4 with an empty files array and a nonzero size, confirmed GetTorrent and UpdateTorrent both report the torrent as still downloading with this patch, and confirmed they reported it downloaded before the patch, which reproduces Radarr not processing Decypharr symlinks #113/Decypharr symlink issue on qbit mount #122
2. Ran the same test with files populated to make sure a genuinely finished torrent is not affected, still reported downloaded with progress at 100
3. Ran the full test suite (go test ./...) plus go vet and gofmt, all clean

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Risks / Notes

• Only touches AllDebrid's GetTorrent/updateTorrent, other providers aren't affected
• A torrent that genuinely has zero size and zero files still gets treated as downloaded like before, this only changes behavior when the reported size is greater than zero

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Screenshots (if applicable)

N/A

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Checklist

• Code builds successfully
• No console/log errors
• Reviewed my own code
• Target branch is correct