Build improvements

[TranceLove]

Description

Please install NDK 30 (30.0.16248370) before running the build locally.

Changes:

• Pin Rust version to 1.98.1 at Github Actions
• Add rust-toolchain.toml to pin Rust version on local builds
• Github Action use JDK 21
• Bump NDK version to r30 LTS
• Make JDK version specification controllable from libs.versions.toml
• Github Actions workflow files align with release/4.0 branch for latest versions of Github Actions and syntaxes

Issue tracker

Fixes #4551 (hopefully)

Automatic tests

N/A

Manual tests

• Done

• Device:

• OS:

Build tasks success

Successfully running following tasks on local:

• ./gradlew assembledebug
• ./gradlew spotlessCheck

Generative code

• This PR used generative code tools (GenAI, LLMs, etc.)

AI was used in pointing out the use of Rust toolchain overrides rust-toolchain.toml during research.

• Model: Nemo MAX 2.0 (Qwen 3.5, GLM 5.3 as mentioned at https://proton.me/support/lumo-privacy#open-source)
• Provider: Lumo AI by Proton

[TranceLove]

@IzzySoft please see if it helps

[EmmanuelMess]

This really needs a clear way to inform the developer that the NDK version is not the one expected, especially if it needs an exact match. The error message from compilation is really not helpful, as it tells you the NDK library is missing altogether.

[IzzySoft]

please see if it helps

thanks! But with ~1k apps in our builder, I cannot remember all details for each app 🙈 So I first need to figure out "helps with what exactly… Ah, issue linked, thanks!

• we could pick versions for JDK, NDK, from gradle/libs.versions.toml
• I was about to say rust setup could now be automated thanks to your rust-toolchains.toml – but I doubt it will be found in the sub directory. Doesn't rustup expect that in the project root, or the current working directory? OK, guess we could first cd into file_operations I guess. Ah, I see we do that already, to call setup_rust_android.sh.

Guess we'll have to see if the cargo error is gone with the next release then, after this PR has been merged…