feat: Register IEventOutbox as SQLiteEventOutbox in AddSQLiteOutbox()

[samtrion]

User Story

As a developer using SQLite with Pulse, I want IEventOutbox to be registered as SQLiteEventOutbox when AddSQLiteOutbox() is configured, so that events stored via IEventOutbox share the same SQLite connection and transaction as my business logic.

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Background

Mirrors the SQL Server (#230) and PostgreSQL (#231) fixes. SQLiteEventOutbox exists but is not registered in DI, causing applications to fall back to the default OutboxEventStore.

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Requirements

• Update SQLiteEventOutbox to accept SQLiteOutboxOptions as constructor parameter; open SqliteConnection from ConnectionString; enlist in active SqliteTransaction from IOutboxTransactionScope when present.
• In AddSQLiteOutbox(), register IEventOutbox → SQLiteEventOutbox as Scoped.
• Add AddSQLiteOutboxTransactionScope<TUnitOfWork>() convenience extension.
• Update unit tests for SQLiteEventOutbox to cover the new constructor path.

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Acceptance Criteria

• After AddSQLiteOutbox(), resolving IEventOutbox returns SQLiteEventOutbox.
• SQLiteEventOutbox enlists in the active SqliteTransaction from IOutboxTransactionScope when present.
• SQLiteEventOutbox opens its own connection when no IOutboxTransactionScope is active.
• AddSQLiteOutboxTransactionScope<TUnitOfWork>() registers the UoW as Scoped.
• Unit tests cover: with active transaction scope, without transaction scope.