Add mitigation with task and mapping import

Signed-off-by: gearnode <bryan@frimin.fr>

pkg/coredata/migrations/20250401T165000Z.sql

@@ -0,0 +1,3 @@
+ALTER TABLE mitigations RENAME COLUMN content_ref TO reference_id;
+ALTER TABLE mitigations ADD CONSTRAINT mitigations_org_ref_unique UNIQUE (organization_id, reference_id);
+ALTER TABLE mitigations DROP COLUMN standards;