docs: Reserve BEP-1043 for Scope types description

[fregataa]

resolves #NNN (BA-MMM)

Add BEP-1043 for Scope types description

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 reserves BEP-1043 in the BEP Number Registry for a proposal about Scope types description. Following the established process, this reserves the number before creating the actual BEP document.

Changes:

• Added BEP-1043 entry to the BEP Number Registry table

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[Copilot]

The title "Scope types description" does not follow the established Title Case convention used throughout the BEP registry. All other BEP titles use Title Case where important words are capitalized (e.g., "Agent Architecture", "Fair Share Scheduler", "GraphQL API Field Metadata Extension"). The title should be "Scope Types Description" to maintain consistency with the codebase conventions as seen in lines 91-132.