Replace implemented column with CMMI maturity level

Drop the boolean implemented/not-implemented state in favor of a
mandatory CMMI maturity level enum (NONE, INITIAL, MANAGED, DEFINED,
QUANTITATIVELY_MANAGED, OPTIMIZING) stored as a Postgres enum type.

The migration backfills existing rows (NOT_IMPLEMENTED → NONE,
IMPLEMENTED → INITIAL), makes the column NOT NULL, and drops the old
implemented column and its enum type.

- maturityLevel is required on CreateControlInput and non-nullable (!)
  in the GraphQL schema
- CLI displays human-readable CMMI labels instead of raw enum tokens
- SOA table and published document use a single Maturity column in
  place of the old Implemented + Maturity columns
- Remove ControlImplementationState type and all implemented references
  across backend, frontend, CLI, MCP, n8n, and E2E tests

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

packages/n8n-node/nodes/Probo/actions/control/get.operation.ts

@@ -46,7 +46,6 @@ export async function execute(
 					sectionTitle
 					name
 					description
-					implemented
 					notImplementedJustification
 					maturityLevel
 					createdAt

packages/n8n-node/nodes/Probo/actions/control/getAll.operation.ts

@@ -81,7 +81,6 @@ export async function execute(
 								sectionTitle
 								name
 								description
-								implemented
 								maturityLevel
 								createdAt
 								updatedAt