Clean child sessions in iam membership migration

Signed-off-by: Émile Ré <emile@getprobo.com>

pkg/coredata/migrations/20260119T182800.sql

@@ -50,13 +50,24 @@ updated_profiles AS (
         old_to_new m
     WHERE
         mp.membership_id = m.old_id RETURNING id
-)
+),
-DELETE FROM
+deleted_memberships AS (
+    DELETE FROM
         iam_memberships
-WHERE
+    WHERE
         id IN (
             SELECT
                 old_id
             FROM
                 old_to_new
-    ) RETURNING id;
+        ) RETURNING id
+)
+DELETE FROM
+    iam_sessions
+WHERE
+    membership_id IN (
+        SELECT
+            old_id
+        FROM
+            old_to_new
+    );