CBG-4853: Cut release/4.0.0 and move main to 4.1

[bbrks]

CBG-4853

• Cut 4.0.0 release branch and bump main to next minor version

[github-actions]

Redocly previews

• Admin API
• Public API
• Metric API
• Diagnostic API

[Copilot]

Pull Request Overview

Bumps project version from 4.0.x to 4.1.x on main and creates a 4.0.0 release manifest.

• Updates version identifiers in manifests, Go code, and OpenAPI specs to 4.1.
• Adds a dedicated 4.0.0 release manifest (manifest/4.0.xml) and corresponding product-config entry.
• Resets start_build for new 4.1 cycle and archives 4.0.0 build settings.

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
manifest/product-config.json	Sets main line to 4.1.0 and adds 4.0.0 release entry.
manifest/default.xml	Bumps VERSION annotation to 4.1.0.
manifest/4.0.xml	Adds pinned manifest for 4.0.0 release branch.
docs/api/public.yaml	Updates API version string to 4.1.
docs/api/metric.yaml	Updates API version string to 4.1.
docs/api/metric-capella.yaml	Updates API version string to 4.1.
docs/api/diagnostic.yaml	Updates API version string to 4.1.
docs/api/admin.yaml	Updates API version string to 4.1.
docs/api/admin-capella.yaml	Updates API version string to 4.1.
base/version.go	Updates ProductAPIVersionMinor to 1 (4.1).