feat(education): submit sessions and persist reports

sql/mysql/education/004-education-submit-report-rollback.sql

@@ -0,0 +1,42 @@
+-- =============================================
+-- Education 模块 — Ticket #8 迁移回滚
+-- 004-education-submit-report-rollback.sql
+-- =============================================
+--
+-- WARNING: This file contains NO executable SQL.
+-- Destructive rollback requires manual operator verification.
+--
+-- Manual rollback procedure (operator must execute):
+-- 1. Verify no other tables depend on these tables:
+--      SELECT TABLE_NAME, COLUMN_NAME, REFERENCED_TABLE_NAME
+--        FROM information_schema.KEY_COLUMN_USAGE
+--       WHERE REFERENCED_TABLE_NAME IN ('education_submit_idempotency',
+--            'education_practice_report', 'education_practice_report_detail')
+--         AND TABLE_SCHEMA = DATABASE();
+--    Result MUST be empty before proceeding.
+--
+-- 2. Verify columns are not referenced by application code:
+--    Search codebase for 'correct_answer' / 'explanation' references in
+--    education_practice_question to confirm no other consumers.
+--
+-- 3. Verify the tables contain only data from this migration:
+--      SELECT COUNT(*) AS idempotency_count FROM education_submit_idempotency;
+--      SELECT COUNT(*) AS report_count FROM education_practice_report;
+--      SELECT COUNT(*) AS detail_count FROM education_practice_report_detail;
+--    Operator must confirm these counts are acceptable to destroy.
+--
+-- 4. After verification, execute:
+--      DROP TABLE IF EXISTS education_practice_report_detail;
+--      DROP TABLE IF EXISTS education_practice_report;
+--      DROP TABLE IF EXISTS education_submit_idempotency;
+--      ALTER TABLE education_practice_question
+--          DROP COLUMN correct_answer,
+--          DROP COLUMN explanation;
+--
+-- DO NOT uncomment or execute the lines below without operator verification.
+-- -- DROP TABLE IF EXISTS education_practice_report_detail;
+-- -- DROP TABLE IF EXISTS education_practice_report;
+-- -- DROP TABLE IF EXISTS education_submit_idempotency;
+-- -- ALTER TABLE education_practice_question
+-- --     DROP COLUMN correct_answer,
+-- --     DROP COLUMN explanation;