feat(education): complete Flyway migration and atomic submit

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

@@ -0,0 +1,50 @@
+-- =============================================
+-- Education 模块 — Ticket #8 迁移回滚 (PostgreSQL)
+-- 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
+--          tc.table_name,
+--          kcu.column_name,
+--          ccu.table_name AS referenced_table_name
+--      FROM information_schema.table_constraints AS tc
+--      JOIN information_schema.key_column_usage AS kcu
+--        ON tc.constraint_name = kcu.constraint_name
+--      JOIN information_schema.constraint_column_usage AS ccu
+--        ON ccu.constraint_name = tc.constraint_name
+--      WHERE tc.constraint_type = 'FOREIGN KEY'
+--        AND ccu.table_name IN ('education_submit_idempotency',
+--             'education_practice_report', 'education_practice_report_detail')
+--        AND ccu.table_catalog = current_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;