refactor(BA-3532): Apply action-processor pattern in container registry deletion API

[seedspirit]

resolves #7555 (BA-3532)

Checklist: (if applicable)

• Milestone metadata specifying the target backport version
• Mention to the original issue
• Installer updates including:
  • Fixtures for db schema changes
  • New mandatory config options
• Update of end-to-end CLI integration tests in ai.backend.test
• API server-client counterparts (e.g., manager API -> client SDK)
• Test case(s) to:
  • Demonstrate the difference of before/after
  • Demonstrate the flow of abstract/conceptual models with a concrete implementation
• Documentation
  • Contents in the docs directory
  • docstrings in public interfaces and type annotations

[Copilot]

Pull request overview

This PR refactors the container registry deletion API to follow the action-processor pattern, replacing direct database operations in GraphQL mutations with a structured service layer approach. This improves code organization, maintainability, and consistency with other container registry operations.

Key changes:

• Introduced DeleteContainerRegistryAction and associated components following the action-processor pattern
• Migrated GraphQL mutations (both v1 and v2) from direct database operations to use the new action processor
• Added comprehensive test coverage for the deletion functionality

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/ai/backend/manager/services/container_registry/actions/delete_container_registry.py	New action definition for container registry deletion with action and result dataclasses
src/ai/backend/manager/services/container_registry/service.py	Added delete_container_registry service method that delegates to repository
src/ai/backend/manager/services/container_registry/processors.py	Registered delete action processor and added to supported actions list
src/ai/backend/manager/repositories/container_registry/repository.py	Implemented delete_registry repository method with proper error handling
src/ai/backend/manager/models/gql_models/container_registry.py	Refactored DeleteContainerRegistryNode mutation to use action-processor pattern
src/ai/backend/manager/models/gql_models/container_registry_v2.py	Refactored DeleteContainerRegistryNodeV2 mutation to use action-processor pattern
tests/manager/repositories/container_registry/test_container_registry_repository.py	Added test fixtures and three test cases for delete functionality
changes/7559.enhance.md	Changelog entry documenting the enhancement

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[HyeockJinKim]

Please check test failure (In merge queue) @seedspirit