RDSC-5587 Update CLI public docs and changelog

[stoyanr]

See https://redislabs.atlassian.net/browse/RDSC-5587, the RDI PR is https://github.com/RedisLabs/redis-data-integration/pull/2657.

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Note

Low Risk
Documentation-only changes to RDI integration guides and CLI reference; no application code or runtime behavior is modified.

Overview
This PR realigns RDI public docs with the current redis-di CLI (API URL, contexts, and REST-backed commands) and drops legacy install/ops commands from the reference.

The CLI reference is rewritten: global options (--api-url, JWT vs Redis Cloud auth, ~/.redis-di contexts with set-context / use-context), command groupings, and new pages for list/get/describe, delete, secrets CRUD, DLQ commands (list-dlqs, list-dlq-records; get-rejected as alias), jobs/metrics, and completion. Removed reference pages include add-context, install, upgrade, monitor, trace, and the old standalone status / get-rejected docs.

Deploy and operations guides now center on the CLI: unified set-secret for all install types (replacing rdi-secret.sh), secret management commands, deploy flags (--dry-run, validation, --start), lifecycle (describe, start/stop/reset/delete), and --wait / --timeout behavior for batched secret updates. K8s kubectl secret docs add required operator discovery labels and recommend the CLI over raw kubectl.

Installation and troubleshooting updates add a separate CLI download section for Kubernetes, VM note that the CLI is bundled (optional off-box download), redis-di info for API checks, quick-start context flow via --api-url, DLQ/observability links to describe, and upgrade recovery text clarifying upgrade.sh vs deprecated redis-di upgrade.

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[CLAassistant]

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[andy-stark-redis]

LGTM - great update :-)