Feat/dart precompiled binary

[BitcoinZavior]

Details

Precompiled Binaries Feature

Resolves #1308
This PR introduces a comprehensive precompiled binaries system that significantly improves the developer experience by reducing build times and providing secure, signed artifacts.

Key Features

Secure Distribution

• Ed25519-signed precompiled binaries with public key verification
• Automated signing and verification pipeline
• Secure artifact hosting via GitHub Releases

Performance Improvements

• Skip local Rust compilation for supported platforms
• Automatic fallback to local builds when precompiled binaries unavailable
• Configurable modes: auto, always, or never

Developer Experience

• Zero-configuration setup for most users
• Comprehensive CLI tooling for maintainers
• Detailed documentation and troubleshooting guides

Configuration

Users can configure precompiled binaries in their pubspec.yaml:
Defaulting to auto which most users would want.

payjoin_dart:
  precompiled_binaries:
    mode: auto  # auto | always | never

Done the old fashioned way without AI

Pull Request Checklist

Please confirm the following before requesting review:

• I have disclosed my use of
  AI
  in the body of this PR.
• I have read CONTRIBUTING.md and rebased my branch to produce hygienic commits.

[coveralls]

Pull Request Test Coverage Report for Build 21574637307

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 83.203%

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Totals
Change from base Build 21447062880:	0.0%
Covered Lines:	10140
Relevant Lines:	12187

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💛 - Coveralls

[DanGould]

Whoa, massive PR! Thanks for your contribution.

I am curious about the history first. Having a bit of trouble understanding how this came together piece by piece because as far as I can tell each commit does not build on the previous one (in that I can run some code at each stage and see it evolve from a simple MVP to a full blown precompilation software tooling suite). Can you help me understand what each piece does?

One example of something I'm confused about is the dart CLI to build. What does that do that benefits from dart tooling vs some universal tooling that could work across projects (if that's even possible, I really don't know).

This is going to be really hard to review as 6k lines. Is there any intermediate step that or guidance you could give me to make this easier to review?

CI failure is OK for a start but we'll have to address that to merge, too.

[DanGould]

? why include this commit

[DanGould]

Shouldn't the SOP be to get this from pub.dev? Why mention path?

[DanGould]

I don't think this file exists as of commit 1e57740 where this is introduced

[BitcoinZavior]

Oops, yes, adding it now.

[DanGould]

May you explain the purpose of this file? I'm new to precompiled binaries and it's not readily apparent what this is for. If the rationale was left in a the commit log it'd be super helpful for review.