rust-toolchain.toml pins a version with no documented upgrade cadence

[yusuftomilola]

contracts/rust-toolchain.toml pins a specific Rust toolchain version but there's no note on how often it should be bumped or what triggers a bump (e.g. following soroban-sdk's supported toolchain). Add a short note in the README.

[guptakumarranjeet150]

Hello team,

I would like to resolve this issue. Here is my proposed execution plan:

• Implementation: Structure Soroban contract handlers for rust-toolchain.toml pins a version with no documented upgrade cadence following project idioms and storage invariants.
• Testing: Ensure contract compiles cleanly and passes all cargo tests without warnings.

Looking forward to collaborating on this—please assign!

[guptakumarranjeet150]

Hello @maintainers,

I am interested in working on this issue.
Plan:

1. Implement rust-toolchain.toml pins a version with no documented upgrade cadence with explicit require_auth checks, secure state storage, and gas optimization.
2. Add Soroban test cases checking unauthorized invocations, edge values, and state updates.

I am ready to start immediately—please feel free to assign this to me!