Add data-migration tracking; prevent subtitle dedup

Track and run run-once SQL data migrations: entrypoint now checks _data_migrations before executing each prisma data-migration file, records successful runs, and skips already-applied scripts. Adds a Prisma DataMigration model mapped to _data_migrations and a new reset-works-table.sql migration to clear work tables for a dedup rebuild. Also improves dedup logic: extractSubtitle and subtitle-compatibility checks are added so series entries like "Series: Book A" vs "Series: Book B" are not collapsed, with accompanying unit tests for extraction and behavior.

prisma/schema.prisma

@@ -718,3 +718,15 @@ model AudibleCacheCategory {
   @@index([categoryId, rank])
   @@map("audible_cache_categories")
 }
+
+// ============================================================================
+// DATA MIGRATION TRACKING
+// Tracks which data migration SQL scripts have been executed (run-once).
+// ============================================================================
+
+model DataMigration {
+  name       String   @id
+  executedAt DateTime @default(now()) @map("executed_at")
+
+  @@map("_data_migrations")
+}