Add "restore version as new latest" with deprecation support for AI Catalog items

Summary

Allow item owners to restore an older released version as a new latest version, with the ability to mark the replaced version as deprecated. Deprecated versions are excluded from consumer version selection.

Parent issue: gitlab-org/gitlab#596982

Changes

DB migration

• Add deprecated boolean column to ai_catalog_item_versions (default: false, not null)

Model (ee/app/models/ai/catalog/item_version.rb)

• Add scopes: not_deprecated, released
• Allow updating deprecated on released versions (bypass validate_readonly for this field)

GraphQL schema

• Expose deprecated field on VersionInterface
• Add optional exclude_deprecated filter to ItemVersionsFinder

New service: Ai::Catalog::ItemVersions::RestoreService

• Copy definition and schema_version from source version into a new version record
• Bump version number (minor) from latest released
• Set release_date, created_by, update latest_version and latest_released_version on item
• Optionally mark current latest as deprecated (default: true)
• Wrap in transaction

New GraphQL mutation: AiCatalogItemVersionRestore

• Arguments: id (version to restore from), deprecate_current (boolean, default true)
• Returns: newly created ItemVersion
• Authorization: admin_ai_catalog_item (Maintainer/Owner of owning project)

Audit events

• Add relevant audit events