[STACKED on #956] fix(kms): align Node authorization safety

[kvinwang]

STACKED PR — merge #956 first.

Problem

Node-based authorization did not apply the same input, failure, and trust-safety checks as the other backend path. Backend errors or malformed decisions could be interpreted inconsistently, including unsafe fallback behavior.

Root cause and fix

Normalize Node authorization results through the same fail-closed validation and decision contract used by KMS.

Implementation

The branch records the following focused implementation work:

• fix(kms): align Node authorization safety
• fix(test): isolate Node authorization mocks
• fix(kms): align Node authorization build entrypoint
• fix(kms): align authorization validation errors
• fix(kms): narrow authorization validation errors
• fix(kms): resolve test upgrade artifacts
• fix(kms): align authorization container runtime

Changed paths:

• dstack/kms/auth-eth-bun/index.test.ts
• dstack/kms/auth-eth-bun/index.ts
• dstack/kms/auth-eth/script/Upgrade.s.sol
• dstack/kms/auth-eth/src/main.test.ts
• dstack/kms/auth-eth/src/server.ts
• dstack/kms/auth-eth/tsconfig.json
• dstack/kms/dstack-app/compose-dev.yaml
• dstack/kms/dstack-app/docker-compose.yaml

Scope

This PR addresses one logical kms finding. It intentionally excludes the acceptance-test infrastructure from #841 and unrelated product fixes from #840.

Dependency and merge order

• Parent PR: [STACKED on #953] fix(kms): redact the authorization backend endpoint #956
• GitHub base branch: codex/fix-kms-auth-endpoint-redaction
• Merge the parent first; this PR contains only the additional delta above that parent.

Verification

• git diff --check origin/codex/fix-kms-auth-endpoint-redaction..origin/codex/fix-kms-node-auth-safety: passed.
• The declared base was verified as an ancestor of the PR head.
• Focused compile/check verification was run for the changed component where applicable; non-Rust packaging or configuration changes were reviewed against their exact branch delta.

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