Self-serve operator journey documentation

[swarna1101]

Tracks the full documentation work for the self-serve operator journey. This issue closes when every sub-issue is closed.

Goal

An operator goes from the docs landing page to a connected gateway, and then to Signal and Accelerate, in the same order Console presents it.

• Journey, reference, help and learn live on the public docs site (docs.getoptimum.xyz, this repo).
• Versioned gateway docs stay on getoptimum.github.io/optimum-gateway. Journey pages link to them through versions/latest/. Moving the gateway docs here can happen after launch.
• Source of truth for technical content is the shipped gateway and Console behaviour. The design mockups set layout and intent only.

Acceptance criteria

• An operator can go from the landing page to a connected gateway without leaving the journey.
• Every journey step matches its Console screen in order and naming.
• Every current URL resolves, with redirects for removed pages.
• Gateway links point at versions/latest/, not a pinned version.
• The docs use the terms Signal, Accelerate and "bid cutoff optimization". They never use "timing games" or "Stream" as a product name.
• Someone outside the team completes Parts 1 and 2 on a clean machine without help.

[linear-code]

OPT-1112