Add firefly/eventsourcing: event store, snapshots, projections and event-sourced orchestration

[ancongui]

Adds firefly/eventsourcing, at parity with PyFly's eventsourcing module and modeled on jafly's fireflyframework-eventsourcing.

What ships

• Event store, set by firefly.eventsourcing.store.provider (memory or database).
  • Appends use optimistic concurrency. A version clash on UNIQUE(aggregate_id, version) is translated into a ConcurrencyException.
  • Streams can be read per aggregate (from/to a version) or globally in commit order from a position, filtered by event type, aggregate type or time range.
  • The database store numbers events in commit order on every server, so a reader of a global position never skips an event that commits late.
  • It is proven on PostgreSQL, MySQL, MariaDB, SQL Server and SQLite, including racing appenders: on the same aggregate exactly one wins, and on different aggregates none are lost.
• Events. The event type registry uses #[EventType(type, version)] and is compiled by firefly:cache. Each event's envelope carries metadata (correlation and causation ids, tenant, user, timestamps), filled by metadata contributors. An upcaster chain is applied on read.
• Aggregates. An event-sourced aggregate base, plus a snapshot-aware EventSourcedRepository.
• Snapshots (memory|database): taken every firefly.eventsourcing.snapshot.threshold events, with keep-count retention, and loaded as the latest at or before a version.
• Projections. Function projections and a ProjectionRunner.
  • Checkpoints are stored in a CheckpointStore (memory|database).
  • A lease on the DistributedLock port ensures only one node advances a projection.
  • Runs in catch-up and live modes, and supports reset/rebuild.
  • Lag is reported in an actuator health component.
  • firefly:eventsourcing:projections, :projections:run and :projections:rebuild.
• Publishing. Appended events go to firefly/eda in the same transaction through the database outbox when firefly.eda.provider=database|postgres, otherwise after commit, and never twice (firefly.eventsourcing.publish.enabled, destination).
• Orchestration. firefly.orchestration.persistence.provider=event-sourced stores executions as an aggregate with a snapshot and a projection, and passes W2's provider contract and capstones.
• Tenancy. A TenantScopedEventStore decorator, enabled with firefly.eventsourcing.tenancy.enabled. Tenant ids are compared exactly (binary collation), so tenants never leak across case on MySQL, MariaDB or SQL Server.

Verification

Includes origin/main (PR #17's docs wave).

Run	Result
composer check	exit 0, 6720 passed
Integration on PostgreSQL 16, MySQL 8.4, MariaDB 11 and SQLite, plus the broker lanes (RabbitMQ, Kafka, Redis)	372 passed, 0 failed
SQL Server lane (local container)	145 passed, 0 failed
bash scripts/build-docs.sh	exit 0