[socvic]

Summary

• add threshold-signer pause and unpause requests with policy-version invalidation, terminal execution, and monotonic state versions
• block withdrawal proposal, approval, execution, and governance-authorized withdrawal while preserving deposits, reads, cancellation, and recovery
• document incident evidence and the threshold-authorized recovery procedure

Verification

• cargo test -p stellar-sentinel-treasury

Closes #81

[xqcxx]

The pause implementation and its authorization boundaries look sound on review. Please rebase or resolve the current merge conflicts against the base branch before this can be approved and merged; GitHub reports this PR as UNSTABLE.

[socvic]

Verified against the current upstream base: this branch is already based on main at f01ac31, and GitHub currently reports it as mergeable with no conflict to resolve. No rebase was needed because there are no newer base commits. Please re-review when the mergeability status refreshes.