Prepare Server537 archive/restore release with Web190 and Engine350

[chen21019]

Summary

• Prepare Server v1.6.537 with Web Console 1.6.190 and Engine v0.183.350 for persistent Stack/Service archive and restore.
• Pin exact producer commits and artifact hashes; independently verify the Engine350 Jar and both retained frozen-schema hashes.
• Preserve the pinned Server460 base, other component identities, update/RBAC/Key policy boundaries, authentication, volumes and performance overrides.
• Keep README/compatibility/performance explicitly candidate-only with ordinary numeric install tags. Server537 image/producer/digests/publication remain pending.
• Advance security release metadata only; all 69 VEX statements, 11 vendor findings/22 package rows and policy/review deadlines are unchanged.

Validation

• Published/candidate install contract: 15 tests passed.
• Directly affected packaging contract: 8 focused tests passed.
• Three changed shell files: bash -n passed; git diff --check passed.
• Engine350 cattle.jar: 87,906,638 bytes, SHA-256 637ddaa42cd93c019b4d0813d7053b71dc42797a7f3ac2aa4b10fcc7e304cb31; nested readonly/restricted schema bytes were independently read and matched their guards.
• The candidate release note preserves precise earlier isolated feature evidence rather than claiming final Server artifact or company-production acceptance.

Dependency and publication gate

Web190 publication/anonymous artifact readback has passed. Engine350 official publication and anonymous SHA-256 readback are required before this PR is merged. Do not bypass required source/CodeQL checks. After dependency readback and a normal protected-branch merge, dispatch the existing publish-current-server.yml workflow from main with release_tag=v1.6.537; do not overwrite any existing tag/artifact. No 8080 deployment, KB or workbook changes are part of this PR.