feat(server): Enqueue jobs in bulk (#5974)

* feat(server): Enqueue jobs in bulk

The Job Repository now has a `queueAll` method, that enqueues messages
in bulk (using BullMQ's
[`addBulk`](https://docs.bullmq.io/guide/queues/adding-bulks)),
improving performance when many jobs must be enqueued within the same
operation.

Primary change is in `src/domain/job/job.service.ts`, and other services
have been refactored to use `queueAll` when useful.

As a simple local benchmark, triggering a full thumbnail generation
process over a library of ~1,200 assets and ~350 faces went from
**~600ms** to **~250ms**.

* fix: Review feedback

server/src/domain/repositories/job.repository.ts

@@ -103,6 +103,7 @@ export interface IJobRepository {
   deleteCronJob(name: string): void;
   setConcurrency(queueName: QueueName, concurrency: number): void;
   queue(item: JobItem): Promise<void>;
+  queueAll(items: JobItem[]): Promise<void>;
   pause(name: QueueName): Promise<void>;
   resume(name: QueueName): Promise<void>;
   empty(name: QueueName): Promise<void>;