feat(updater): silent background download and in-app install progress dialog

[codeiva11]

Summary

Improves the in-app update flow by pre-downloading update APKs quietly in the background and adding an in-app progress dialog during installation.

Key Changes

1. Silent Background Download: In \InAppUpdater.kt, \downloadUpdateSilently\ downloads the update APK to internal cache without throwing foreground notifications while browsing/watching.
2. Post-Download Dialog: The update prompt (Update, Cancel, Skip) is only shown after the file is fully ready, preventing wait times upon clicking Update.
3. In-App Progress Feedback: Added \UpdateProgressActivity\ with layout \update_progress_dialog.xml\ that observes installation progress broadcasted from \PackageInstallerService\ (\PROGRESS_UPDATE_ACTION\ / \STATUS_UPDATE_ACTION), displaying a 0%–100% horizontal progress bar and status text.
4. Local File Staging in Service: Added \installFromFile\ in \PackageInstallerService\ to handle direct session writing from the cached APK file.
5. Compatibility: Preserved legacy installer fallback for MIUI/HyperOS devices.

Verification

• Tested and verified build: ./gradlew assemblePrereleaseDebug\ succeeded (output APK generated).
• Ran ./gradlew library:checkKotlinAbi\ to ensure binary compatibility.

[LagradOst]

Good pull request! Just please be aware that this has already been fixed in #3204

[codeiva11]

"Thanks for the heads-up @LagradOst! I reviewed #3204—the new Compose UI and GithubViewModel refactor look great.

The main enhancement in this PR (#3214) was implementing silent background pre-downloading (downloading the update APK quietly first, then prompting the user so clicking 'Update' triggers immediate installation without download wait-times).

Since #3204 overhauls the updater architecture, I will close this PR and rebase/port the silent background pre-download & cached installation logic directly onto your #3204 Compose branch (GithubViewModel / ApkUpdater)."

[codeiva11]

Thanks for the heads-up @LagradOst! I reviewed #3204—the new Compose UI and GithubViewModel refactor look really clean.

The main intent behind this PR was introducing silent background pre-downloading (fetching the update APK quietly in the background first, so that when the update prompt is shown, clicking 'Update' installs immediately with zero download wait time).

Since #3204 refactors the entire updater foundation, I will close this PR and port the silent background pre-download & cached install logic on top of your #3204 Compose branch.