fix(console): require secure session key entropy

[GatewayJ]

Type of Change

• New Feature
• Bug Fix
• Documentation
• Performance Improvement
• Test/CI
• Refactor
• Other:

Related Issues

Closes rustfs/backlog#1092

Summary of Changes

• Generate fallback Console session keys exclusively with ring::rand::SystemRandom.
• Fail Console startup when cryptographically secure randomness is unavailable.
• Remove the predictable timestamp-and-process-ID hash fallback and add a regression test for generated key shape and uniqueness.

The previous entropy fallback could produce a guessable session signing key if /dev/urandom could not be read. Deployments with JWT_SECRET configured are unchanged; unconfigured single-process deployments still receive an ephemeral key, now only from a CSPRNG.

Checklist

• I have read and followed the CONTRIBUTING.md guidelines
• Passed make pre-commit (fmt-check + clippy + test + console-lint + console-fmt-check)
• Added/updated necessary tests
• Documentation updated (N/A: no configuration or public API changed)
• CHANGELOG.md updated under [Unreleased] (N/A: no changelog file exists in the repository)
• CI/CD passed (pending upstream CI)

Impact

• Breaking change (CRD/API compatibility)
• Requires doc/config/deployment update
• Other impact: Console startup now fails instead of using weak entropy when the system CSPRNG is unavailable.

Verification

make pre-commit

Additional Notes

The chart-provided JWT_SECRET path remains the recommended deployment configuration.

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