Introduce `implemented` enum (IMPLEMENTED/NOT_IMPLEMENTED) and
`not_implemented_justification` (nullable text) fields on the Control
entity across all API surfaces (GraphQL, MCP, CLI), database, frontend,
and SOA export.
The database stores implementation state as a PostgreSQL enum
`control_implementation_state`. Controls default to IMPLEMENTED during
migration. The SOA list and PDF export show implementation status
alongside applicability, with "-" for non-applicable controls.
Justification columns are renamed for clarity: "Justification for
non-applicability" and "Justification for non-implementation".
Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>
