feat: Migrate JdbcTransactionProvider to ColumnMappedJdbcStateProvider + optional paymentAccount JDBC

[fupelaqu]

Changes

• JdbcTransactionProvider: Migrated from JSON-blob JdbcStateProvider to ColumnMappedJdbcStateProvider with 42 typed columns, using case class TransactionRow to bypass Scala 2's 22-element tuple limit
• paymentAccountToJdbcProcessorStream: Made optional (default None) in SoftPayApi — downstream projects (e.g., license-server) that don't need payment account JDBC no longer need to provide one
• TransactionToJdbcProcessorStream: Updated to use State2ExternalProcessorStream pattern with Flyway migration
• StripeEventHandler: LRU dedup set (LinkedHashMap) replaces ConcurrentHashMap half-clear strategy
• StripeRecurringPaymentApi: automatic_tax opt-in via metadata + metadata propagation to Stripe subscription
• Version: 0.9.3, genericPersistence → 0.8.4

Flyway Migration

db/migration/transaction/V1__create_transaction.sql — 42-column CREATE TABLE with indexes

Part of Story 5.11 (SoftPayment & Stripe Integration).