fix: normalize domain/email columns with citext

Signed-off-by: Yash Gupta <yash3144@gmail.com>

pkg/coredata/migrations/20260111T211335Z.sql

@@ -0,0 +1,8 @@
+ALTER TABLE auth_saml_configurations
+    ALTER COLUMN email_domain TYPE CITEXT;
+
+ALTER TABLE peoples
+    ALTER COLUMN primary_email_address TYPE CITEXT;
+
+ALTER TABLE peoples
+    ALTER COLUMN additional_email_addresses TYPE CITEXT[];