feat: Add real progress visibility to replace spinner-only sideload UX

[Zi-kiki]

Summary

• Replace the spinner-only install experience with real progress visibility.
• Add backend-driven operation progress events and frontend progress state handling.
• Introduce weighted stage progression so long phases (especially transfer) contribute proportionally.
• Add byte-level transfer tracking (uploaded / total) for accurate large-file progress.
• Improve signing-phase progression behavior for long-running large IPA signing.

Why

In the original implementation, users only saw a loading spinner during installation with no indication of actual progress. For large IPA packages, this creates long periods of uncertainty and a poor installation experience.

[nab138]

I like the concept, but I tested this out and it seems to be a little rough around the edges still, at least for the SideStore operations.

Here, it says completed and triggeres the operation completed screen before its actually finished:

Also here, it says "Please wait..." and "Preparing..." even though everything is done.

[Zi-kiki]

Thanks for the report — root cause was on my side.

The progress system was originally designed mainly for the Import IPA path. During that work, I optimized heavily for large-package sideload UX, but I didn’t fully validate all other operation flows, which caused completion-state inconsistencies (e.g. showing “Preparing” after done) and extra indicator behavior in some scenarios.

I've addressed the issues mentioned in the previous review.

Additionally, I've added a cancel button (currently hidden).
It is debug-only and intended for QA/testing in China, where Apple ID login can be very slow. It allows quickly dismissing the operation modal without restarting the app and re-logging in.

[nab138]

I don't mean to be nitpicky but there are several things I noticed:

For me, installing sidestore hangs here now. It worked before this PR.

If I unplug my device during the download, I would expect it to fail during the sign & install step, but it instead skips straight to place pairing file and shows the error there. Additionally, the error suggestions added in the previous update of iloader aren't shown.

In addition, the sidestore operation doesn't seem to actually take into account the progress during the sign and install step, which I think would be the most beneficial to show progress for. Also, I'd prefer if all three steps of the operation would be shown at the same time, like the old operation screen, instead of showing only the progress bar and the current step.

Based on the writing in this PR, I'm assuming this code was mostly ai generated, I don't have time to keep testing and giving feedback on ai generated code, so please manually make sure everything works before I look at this again.

[Zi-kiki]

Thanks for the feedback!

The UI issues you mentioned have been fixed.

Regarding the first issue — installing SideStore getting stuck at "Place pairing file":
I tested extensively on iOS 26.3 and 26.4.1 using iPhone 17 Pro and iPad Pro. I could not reproduce the hang, neither with plain SideStore nor SideStore + LiveContainer.

I also deliberately tested various failure scenarios (download phase, transfer phase, install phase, and Place pairing file phase). Error handling and display now work correctly in all cases.

Most of the code (especially the UI part) was generated with Claude 4.6 Opus. Since I'm a high school student and my English isn't very strong, I asked AI to help translate messages.