[feat] add initial database schema with tables, triggers, and views

database/main/trg_requirement_check_attr_insert.sql

@@ -0,0 +1,10 @@
+CREATE TRIGGER trg_requirement_check_attr_insert
+BEFORE INSERT ON requirement
+WHEN NEW.req_type = 'ATTR_MIN'
+BEGIN
+  SELECT CASE
+    WHEN NEW.req_id IS NULL OR NOT EXISTS (SELECT 1 FROM attribute WHERE id = NEW.req_id)
+    THEN RAISE(ABORT, 'requirement.req_id must reference attribute.id for ATTR_MIN')
+  END;
+END;
+