chore: bump proxy to 0.3.2

[AnthonyRonning]

Summary

• bump maple-proxy from 0.3.1 to 0.3.2
• bump the published Rust opensecret SDK from 3.6.1 to 3.6.2
• keep Cargo.lock and the README installation example aligned

This lets API-key proxy traffic inherit the SDK-owned, single-attempt recovery for purged encrypted sessions while preserving the proxy request bytes and avoiding another retry layer in maple-proxy.

Validation

• cargo fmt --all -- --check
• cargo check --locked --all-targets --all-features
• cargo clippy --locked --all-targets --all-features -- -D warnings
• cargo test --locked --all-features: 27 passed
• cargo doc --locked --no-deps --all-features with warnings denied
• cargo package --locked: 12-file package boundary verified
• cargo publish --dry-run --locked verified maple-proxy@0.3.2
• cargo tree resolves opensecret@3.6.2
• git diff --check

The published opensecret@3.6.2 artifact was used for validation. This PR does not publish the crate or create the v0.3.2 release tag.