feat(stablecoin): expose permissionless poke transactions

[3esmit]

Summary

• add typed planners for permissionless stability-fee, redemption-rate, and combined global refresh transactions
• expose wallet-backed module methods with exact account ordering and caller-only signing
• enforce strict redemption-rate preflight while preserving refresh best-effort and frozen-protocol behavior
• cover Rust FFI, module orchestration, failure mapping, generated API, and headless dispatch

Stacked on #339.

Validation

• cargo +nightly fmt --all -- --check
• taplo fmt --check .
• RISC0_SKIP_BUILD=1 cargo +1.94.0 clippy --workspace --all-targets -- -D warnings
• make clippy-guest
• RISC0_DEV_MODE=1 cargo +1.94.0 test --workspace --exclude integration_tests
• RISC0_DEV_MODE=1 cargo +1.94.0 test -p integration_tests
• IDL drift check
• nix build path:.#stablecoin_ffi --no-link
• nix build path:.#stablecoin-module --no-link
• nix build path:.#stablecoin-module-tests --no-link
• logoscore module inspection and call smoke tests

Closes #328

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