Valkey Replacement in Omnibus Single Node and Omnibus HA
## Milestones
* **Feb 2026 (18.9)** - Valkey is bundled as opt-in replacement for Redis. Users can switch from Redis to Valkey. Valkey-specific settings are nice-to-have but not a blocker. Light docs covering the switch process. Valkey Sentinel in place
* **May 2026 (19.0)** - Valkey becomes the default, Redis binaries are removed. Valkey settings added and documented, but existing redis\[\*\] settings remain functional and are honored for backwards compatibility.
* **May 2027 (20.0)** - Redis settings (redis\[\*\]) are removed entirely, all code references switched to Valkey.
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