refactor(vault): clean up inline crate imports

[hpmaxi]

Summary

No related issue. Clean up remaining inline crate:: module and type references across async-vault contracts and tests in favor of top-of-file imports.

Changes

• Import epoch at module level in deposit.rs and redeem.rs.
• Import treasury at module level in redeem.rs.
• Import VaultError directly in test/mod.rs.

Test plan

Automated tests

1. Run contract tests: cargo test -p async-vault
2. Run full workspace tests: cargo test

Manual verification

None.

Breaking changes

None.

Checklist

• Self-reviewed my own diff
• Tests added or updated
• Docs updated (if applicable)
• No unrelated changes bundled in

Screenshots

None.

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Project	Deployment	Actions	Updated
strata-vault-kit-app	Ready	Preview	Sep 25, 2026 6:08pm UTC