chore add core rust project files and diesel migrations

Track required workspace crates, scripts, and historical diesel migrations so the repository contains the complete runnable backend baseline.

Made-with: Cursor

htyws_models/migrations/2022-08-07-144418_refactor_kecheng_tbl/down.sql

@@ -0,0 +1 @@
+-- This file should undo anything in `up.sql`

htyws_models/migrations/2022-08-07-144418_refactor_kecheng_tbl/up.sql

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+-- Your SQL goes here
+
+alter table kecheng
+    rename column group_id to kecheng_teacher_id;
+
+alter table kecheng
+    alter column kecheng_teacher_id set not null;
+
+alter table kecheng
+    drop column teacher_id;
+
+alter table kecheng
+    rename to kecheng_student;
+
+alter table kecheng_student
+    add constraint kecheng_student_kecheng_teacher_id_fk
+        foreign key (kecheng_teacher_id) references kecheng_teacher;
+