Pass contract options correctly

[fbac]

Require explicit config.ContractsOptions and payer private key in migrator.NewMigrationService and migrator.setupBlockchainPublisher to pass contract options correctly during migration setup

This refactor removes contracts from migration server config and makes the migrator require contract options and the payer private key explicitly.

• Add contracts to DBMigratorConfig, introduce migrator.WithContractsOptions, and make migrator.NewMigrationService return error "contracts are required" when missing in migrator.go
• Change migrator.setupBlockchainPublisher to accept payerPrivateKey string and *config.ContractsOptions; update internal references and pass *cfg to NewBlockchainPublisher in builder.go
• Remove Contracts from config.MigrationServerOptions in migration.go
• Pass migrator.WithContractsOptions(&cfg.Options.Contracts) from the server when migration is enabled in server.go
• Update tests to provide contracts via migrator.WithContractsOptions in migrator_test.go

📍Where to Start

Start with migrator.NewMigrationService and the new WithContractsOptions path in migrator.go, then follow the call into migrator.setupBlockchainPublisher in builder.go.

---

Macroscope summarized c65bb3e.

[graphite-app]

How to use the Graphite Merge Queue

Add either label to this PR to merge it via the merge queue:

• Queue - adds this PR to the back of the merge queue
• Hotfix - for urgent hot fixes, skip the queue and merge this PR next

You must have a Graphite account in order to use the merge queue. Sign up using this link.

An organization admin has enabled the Graphite Merge Queue in this repository.

Please do not merge from GitHub as this will restart CI on PRs being processed by the merge queue.