feat(proxy-curator): add Soroban curator operations proxy

[carrion256]

Summary

• Add a typed Soroban curator operations proxy crate for vault runtime maintenance/allocation calls.
• Forward governance submit/accept/revoke/view calls through the governance contract instead of deopaquing governance in the proxy.
• Add package checks, workspace membership, lockfile entry, and ignore generated Soroban test snapshots.

Verification

• cargo check -p templar-curator-proxy-soroban --tests
• cargo test -p templar-curator-proxy-soroban --tests
• cargo check -p templar-curator-proxy-soroban -p templar-4626-proxy-soroban -p templar-soroban-runtime -p templar-soroban-governance --tests
• just check-curator-proxy

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✨ Finishing Touches

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• Commit unit tests in branch refactor/curator-proxy

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[carrion256]

Superseded by the SPR-managed stack: #417 -> #418 -> #419.