feat(education): complete Flyway migration and atomic submit

sql/postgresql/education/002-education-practice-session-rollback.sql

@@ -0,0 +1,32 @@
+-- =============================================
+-- Education 模块 — 练习会话与题目快照回滚
+-- Ticket #6 / Migration 002
+-- =============================================
+--
+-- WARNING: This file contains NO executable SQL.
+-- Destructive rollback (DROP TABLE) 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
+--        FROM information_schema.table_constraints tc
+--        JOIN information_schema.key_column_usage kcu
+--          ON tc.constraint_name = kcu.constraint_name
+--        JOIN information_schema.constraint_column_usage ccu
+--          ON tc.constraint_name = ccu.constraint_name
+--       WHERE tc.constraint_type = 'FOREIGN KEY'
+--         AND ccu.table_name IN ('education_practice_session', 'education_practice_question');
+--    Result MUST be empty before proceeding.
+--
+-- 2. Verify the tables contain only data from this migration:
+--      SELECT COUNT(*) AS session_count FROM education_practice_session;
+--      SELECT COUNT(*) AS question_count FROM education_practice_question;
+--    Operator must confirm these counts are acceptable to destroy.
+--
+-- 3. After verification, execute:
+--      DROP TABLE IF EXISTS education_practice_question;
+--      DROP TABLE IF EXISTS education_practice_session;
+--
+-- DO NOT uncomment or execute the lines below without operator verification.
+-- -- DROP TABLE IF EXISTS education_practice_question;
+-- -- DROP TABLE IF EXISTS education_practice_session;