feat: add TTR simulator and calculation engine, enhance member model with TTR adjustment constant

backend/migrations/20261005_add_hidden_test_user_flags.sql

@@ -0,0 +1,5 @@
+-- Hidden application-review users do not appear in club member/user lists
+-- and must never receive outgoing emails.
+ALTER TABLE `user`
+  ADD COLUMN `is_hidden` TINYINT(1) NOT NULL DEFAULT 0,
+  ADD COLUMN `suppress_emails` TINYINT(1) NOT NULL DEFAULT 0;

backend/migrations/20261005_add_member_ttr_adjustment_constant.sql

@@ -0,0 +1,2 @@
+ALTER TABLE `member`
+  ADD COLUMN `ttr_adjustment_constant` DECIMAL(6,2) NOT NULL DEFAULT 16;