Add UNKNOWN and NOT_IMPLEMENTED measure states

Introduce two new measure states across the full stack: database
migration, Go coredata, GraphQL schema, MCP specification, and
frontend UI (labels, badge variants, and colors).

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/coredata/migrations/20260401T120000Z.sql

@@ -0,0 +1,16 @@
+-- Copyright (c) 2025-2026 Probo Inc <hello@getprobo.com>.
+--
+-- Permission to use, copy, modify, and/or distribute this software for any
+-- purpose with or without fee is hereby granted, provided that the above
+-- copyright notice and this permission notice appear in all copies.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+-- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+-- AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+-- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+-- LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+-- OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+-- PERFORMANCE OF THIS SOFTWARE.
+
+ALTER TYPE mitigation_state ADD VALUE IF NOT EXISTS 'UNKNOWN';
+ALTER TYPE mitigation_state ADD VALUE IF NOT EXISTS 'NOT_IMPLEMENTED';