Add draft CIP for SV governance voter authority

[ericmann]

Summary

This draft CIP proposes a first-class SV governance-voter authority path for non-operational governance votes.

The proposal preserves one-vote-per-SV semantics while separating governance voting from node-operation authority. It defines an SvGovernanceVoter binding, governance-voter request/cast choices, vote attribution fields, a hardcoded Phase 1 action allowlist, and the expected compatibility path for CIP-0103-style external submission.

Notes for reviewers

This is a Draft PR for review and discussion. The draft intentionally leaves several maintainer-owned questions open, including binding uniqueness enforcement, creation guarding, VoteRequest read/disclosure packaging, Vote migration shape, and SRARC_OffboardSv inclusion.

Reference implementation: canton-network/splice#5533

Test plan

• Editorial review only in this repo.
• Reference implementation reports splice-dso-governance-test-daml/damlTest passing on the linked Splice branch.