Harden security boundaries, storage durability, and release pipeline

[Harsh-2002]

Summary

• harden authentication, authorization, secret handling, outbound network controls, and control/data-plane isolation
• make Object Lock, multipart accounting, metadata mutations, encryption, backup/restore, and node-local storage invariants fail closed and writer-atomic across SQLite, libSQL, Turso, sharding, and test doubles
• harden replication, import, webhook, lifecycle, release automation, installer, container, and web-console boundaries
• add regression, parity, migration, conformance, crash-consistency, and documentation coverage for the changed contracts

Validation

• cargo fmt --all --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo nextest run --workspace --no-fail-fast: 1,184 passed, 1 configured skip
• cargo test --workspace --doc
• web install, lint, browser-path regression, build, and both npm audits: 0 vulnerabilities
• full 15-harness conformance suite
• encryption, notifications, and 49-check master-key rotation E2E
• live failpoint crash consistency plus four-arm multi-point crash suite: 20/20
• release-policy, workflow, installer, Python, ShellCheck, and patch-integrity validation