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/test/test-utils.ts

@@ -77,6 +77,7 @@ export const testApp = {
         deleteCronJob: jest.fn(),
         validateCronExpression: jest.fn(),
         queue: (item: JobItem) => jobs && _handler(item),
+        queueAll: (items: JobItem[]) => jobs && Promise.all(items.map(_handler)).then(() => Promise.resolve()),
         resume: jest.fn(),
         empty: jest.fn(),
         setConcurrency: jest.fn(),