feat(eims): implement POST /v1/bulkRegister

New endpoints:
  POST invoices/eims/bulk-register  { invoiceIds: [...] }  — trigger
  POST eims/webhook/bulk-register                          — MoR's callback

Fundamentally different shape from single register: bulkRegister
answers only {conversationId, status:202} immediately: MoR processes
the array asynchronously and pushes the real per-invoice results
(a mix of accepted/rejected in one array, per the collection's own
examples) to a webhook configured out of band. So this ships as two
halves that don't share a call stack — EimsBulkRegistrationService.
registerBulk() reserves a contiguous block of counters (durable
reservation, same doctrine as single register, extended to N items)
and submits; handleBulkCallback(), invoked by the new
EimsWebhookController whenever MoR gets around to it, settles.

New EimsSystemState.inFlightConversationId is the bulk equivalent of
inFlightInvoiceId — a whole batch outstanding, not one invoice — and
the two markers block each other since they share the same counter
sequence. The conversation id isn't known until MoR's 202 arrives, so
reservation stamps a locally-generated placeholder first (same
commit-before-the-network-call reasoning as single register), then
swaps it for MoR's real id right after — the only value the callback
can actually use to find the batch again.

Only the first invoice in a bulk batch chains via PreviousIrn — every
other item gets an empty string, matching the collection's own
two-invoice example exactly (MoR doesn't expect a batch to chain to
IRNs that don't exist yet at submission time).

Webhook has no auth (MoR has no JWT to send) — the conversation id
embedded in the payload is what stands between this and a forged
callback: an item only ever touches an invoice actually holding that
exact id, and an unknown id is logged and ignored, never applied.

Migration 3580000000000: eims_system_state.in_flight_conversation_id,
invoices.eims_bulk_conversation_id (tags which batch an invoice was
submitted in, so a stuck batch — webhook never arrived — can be found
and reconciled by conversation id). Applied to dev DB and recorded in
freight.migrations directly (idempotent IF NOT EXISTS DDL).

Not live-testable from this sandbox (no route to MoR's real gateway).
Signing the whole array as one envelope, the way single /v1/register
was confirmed live to need despite the collection's raw example
showing no envelope, is the reasonable extension of that confirmed
behavior, not a blind guess — but it has not itself been exercised
against the real gateway. Left for the first live bulk attempt to
confirm, same as every other MoR-facing assumption this integration
has made.

apps/edr-freight-api/src/modules/eims/eims.module.ts

@@ -9,6 +9,7 @@ import { NotificationInboxModule } from "../notification-inbox/notification-inbo
 import { NotificationsModule } from "../notifications/notifications.module";
 import { EimsAuthService } from "./eims-auth.service";
 import { EimsAutoSubmitService } from "./eims-auto-submit.service";
+import { EimsBulkRegistrationService } from "./eims-bulk-registration.service";
 import { EimsCancellationService } from "./eims-cancellation.service";
 import { EimsClientService } from "./eims-client.service";
 import { EimsCredentialsProvider } from "./eims-credentials.provider";
@@ -17,6 +18,7 @@ import { EimsInvoiceRegistrationService } from "./eims-invoice-registration.serv
 import { EimsReceiptService } from "./eims-receipt.service";
 import { EimsSellerCacheService } from "./eims-seller-cache.service";
 import { EimsSignerService } from "./eims-signer.service";
+import { EimsWebhookController } from "./eims-webhook.controller";
 import { EimsReceipt } from "./entities/eims-receipt.entity";
 import { EimsSystemState } from "./entities/eims-system-state.entity";
 
@@ -40,13 +42,14 @@ import { EimsSystemState } from "./entities/eims-system-state.entity";
     // so this stays a plain one-directional import, not a new cycle.
     CompaniesModule,
   ],
-  controllers: [EimsInvoiceController],
+  controllers: [EimsInvoiceController, EimsWebhookController],
   providers: [
     EimsCredentialsProvider,
     EimsSignerService,
     EimsAuthService,
     EimsClientService,
     EimsInvoiceRegistrationService,
+    EimsBulkRegistrationService,
     EimsAutoSubmitService,
     EimsCancellationService,
     EimsReceiptService,
@@ -56,6 +59,7 @@ import { EimsSystemState } from "./entities/eims-system-state.entity";
     EimsAuthService,
     EimsClientService,
     EimsInvoiceRegistrationService,
+    EimsBulkRegistrationService,
     EimsCancellationService,
     EimsReceiptService,
   ],