Rename the self-host container image

[JSONbored]

Problem: The published self-host container image carries the old brand name, and self-hosters pin this image tag in their own deployment configuration.

Area: Infra / Self-host

Proposal: Publish the image under the new name going forward. Keep the old image tag resolving (as an alias of the same build) through an agreed deprecation window, and update the release manifest and self-host documentation to reference the new image.

Deliverables:

• New image published on every release going forward.
• Old tag continues resolving through the deprecation window.
• Self-host documentation updated to the new image name.

Acceptance criteria:

• An existing self-hoster's deployment configuration referencing the old image keeps working, unmodified, for the entire window.

Test scenarios:

• Pull both the old and new image tags during the window and confirm they return equivalent builds.

Resources:

• The release manifest, the self-host release workflow, the example deployment configuration, and the example environment file.

Boundaries:

• Never break an existing self-hoster's pinned image tag before the announced window elapses.

---

Part of #4761.

[linear-code]

JSO-3442