Refactor Domain PK from name to UUID

Background

The `domains` table currently uses its `name` column (VARCHAR) as the primary key. This forces every FK reference and external identifier across the codebase to carry a string name, which makes renames impossible, leaks user-visible names into internal data structures, and complicates RBAC scope handling.

This epic introduces a UUID `id` column to the `domains` table, demotes `name` to a unique constraint, and incrementally migrates downstream layers (API, FK columns, RBAC) to the new identifier.

Sub-stories

D-1: Add UUID `id` column, update ORM/Alembic, add DomainID identifier

D-2: Expose `id` in APIs and migrate identifier from `name` to `id` (REST, GraphQL, SDK, CLI)

D-3: Migrate FK references from `domain_name` to `domain_id` across 9 referencing tables

D-4: Migrate RBAC data and `DomainScope`/scope_binder/permission context logic to `domain_id`

Dependency

1 must merge first; 2, 3, 4 can proceed in parallel afterwards (recommended order 3 → 4 to keep RBAC mapping consistent with FK state).

Related

ScalingGroup track was split into BA-6145.

JIRA Issue: BA-6043