docs(seed): add headers clarifying purpose and sync warning

Both files are intentionally kept separate — V1000 is Flyway-managed
for dev, seed_realistic_dataset is manual for prod/staging. Added
headers to document the relationship and prevent silent divergence.

Author: erichiroshi

seed_realistic_dataset.sql

@@ -1,3 +1,12 @@
+-- ============================================================
+-- PROD/STAGING SEED — execução manual via psql
+-- Uso:
+--   docker exec -i <container> psql -U postgres -d library < seed_realistic_dataset.sql
+--
+-- ⚠️  Manter sincronizado com V1000__dev_seed_data.sql
+--     (seed automático do perfil dev via Flyway)
+-- ============================================================
+
 -- ============================
 -- Categorias
 -- ============================

src/main/resources/db/migration/dev/V1000__dev_seed_data.sql

@@ -1,3 +1,11 @@
+-- ============================================================
+-- DEV SEED — Flyway managed (perfil dev)
+-- Executado automaticamente ao subir o ambiente de desenvolvimento.
+--
+-- ⚠️  Manter sincronizado com seed_realistic_dataset.sql
+--     (seed manual para prod/homologação)
+-- ============================================================
+
 -- ============================
 -- Categorias
 -- ============================