Remove unused columns

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

pkg/coredata/migrations/20260311T171614Z.sql

@@ -0,0 +1,8 @@
+ALTER TABLE
+    iam_memberships DROP COLUMN source,
+    DROP COLUMN state;
+
+ALTER TABLE
+    iam_invitations DROP COLUMN full_name,
+    DROP COLUMN email,
+    DROP COLUMN role;