Backup/restore CLI with optional S3 sink

[antonygiomarxdev]

Objective

Add first-class rango backup and rango restore CLI commands with an optional S3 sink for hub workspaces.

Roadmap Mapping

• Phase: phase:1-durable-substrate
• Milestone: v0.3.0

Scope

In scope:

• rango backup + rango restore
• S3 sink behind a feature flag
• Round-trip integration test

Out of scope:

• Scheduled snapshots
• GCS/Azure sinks

Acceptance Criteria

• CLI commands shipped
• S3 round-trip integration test (e.g. localstack)
• Docs updated

Test Plan

• CLI integration tests
• Localstack S3 e2e test