Update Rust toolchain to 1.92.0 to fix cross 0.2.5 dependency

[Copilot]

• Update rust-toolchain.toml to Rust 1.92.0
• Update all workflow files to pin Rust toolchain to 1.92.0
• Update CI test matrix MSRV from 1.86 to 1.92.0
• Fix test matrix to use ${{ matrix.rust }} variable
• Investigate CI test failure (external service 502 error)
• Trigger CI rerun to verify external service is back up

Original prompt

The CI job fails because it attempts to use the cross 0.2.5 crate, which requires rustc 1.92.0 or newer, but the pipeline only has rustc 1.91.0. This leaves the build fragile and prone to breakage, especially as deps update their MSR (minimum supported Rust version). Recent changes (see PR #139) altered toolchain handling and introduced a rust-toolchain file to improve reproducibility for Android builds, but failed to codify the new minimum Rust version in CI.

Proposed Solution:

• Explicitly set up Rust toolchain 1.92.0 (or newer) early in all CI jobs by adding/adjusting a 'Set up Rust' step in .github/workflows/release.yml.
• Ensure the workflow fails early if rustc is too old, outputting a clear message.
• Ensure this setup matches any rust-toolchain file in the repo.
• (Optional, but ideal for reliability): Add matrix/step to periodically check builds also run against latest stable, to detect MSR creeping earlier.

Example snippet to add/update:

- name: Set up Rust
  uses: actions-rs/toolchain@v1
  with:
    toolchain: 1.92.0
    override: true
    components: rustfmt

Reliability improvements:

• This reduces the risk of silent breakage as dependencies evolve, and ensures local/CI builds agree on toolchain version.
• Failing early and clearly when out of date will prevent hidden pipeline failures and reduce developer friction.

Release note: The MSR for CI and production must be >= 1.92.0.

Danger: Not pinning the Rust version in CI leaves builds exposed to breakage when dependencies raise their MSR, as has just happened with cross 0.2.5. Aligning the workflow with the repo's toolchain file and minimum requirements is essential for production safety.

This pull request was created from Copilot chat.

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[Guardiola31337]

@copilot Tests are failing, could you please check and fix as it sounds like a regression as tests were passing before #139

[Copilot]

@copilot Tests are failing, could you please check and fix as it sounds like a regression as tests were passing before #139

The test failure is not a regression from the Rust toolchain changes. The test test_proof_verification_with_developer_portal failed because the external World ID Developer Portal API returned a 502 Bad Gateway error - this is a transient infrastructure issue with the external service, not caused by the code changes.

My changes only updated Rust toolchain versions in rust-toolchain.toml and workflow files, and didn't modify any test code or application logic. I'll trigger a rerun by pushing an empty commit to re-run CI and verify the external service is back up.