fix(stellar): bump soroban-sdk workspace dependency to 22.0.11

[jerryjuche]

Close #107

PR Title

fix(stellar): upgrade soroban-sdk to latest compatible 22.x and validate reproducible build

Summary

This PR updates the Stellar Soroban SDK dependency to the latest compatible 22.x release and validates the Stellar reproducible build flow under the pinned Rust toolchain.

What changed

• Bumped Cargo.toml to the latest compatible soroban-sdk version in the workspace
• Kept all Stellar crate manifests using the workspace dependency
• Verified build compatibility with rustup run 1.88.0 cargo build --release --target wasm32-unknown-unknown
• Verified Stellar test coverage with rustup run 1.88.0 cargo test --workspace

Validation

• cargo build --release --target wasm32-unknown-unknown passes
• cargo test --workspace passes
• Verified the branch is pushed to origin/fix/soroban-sdk-22x-upgrade

Notes

• No contract source changes were required
• This addresses the reproducible-build failure caused by soroban-sdk 22.0.0 on Rust 1.88
• The change is scoped to the Stellar SDK dependency upgrade and validation

Files changed

• Cargo.toml

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[truthixify]

Huge one, merged. This is the fix that unblocks the WASM build I had marked continue-on-error. Thanks for chasing it down.