feat(customers): allocate portal NUMids, with an audit for reusable ones

Customers created in the staff UI had no NUMid and so could not log in to
my.jorgecuadros.com at all: the id is a CustomerLegacyRef row, not a column,
and create() deliberately writes none.

Allocation is a staff action (POST /customers/:id/portal-access, MANAGER)
rather than part of create, because insurance is expected to move to the
platform before utilities and an insurance-only customer has no reason to
spend a utilities id.

The audit that decides which ids are reusable took three passes. "Owns no
rows" matches nobody -- migration gave all 1,171 NUMids a property and a
transaction. "No transaction in N years" also matches nobody -- every customer
carries a synthetic Jan-1 opening-balance row, so everyone looks active this
year. Subtracting that row is what makes dormancy measurable, and it leaves 4
never-used ids and 10 dormant ones on dev. Two further traps are encoded in the
queries: insurance/DATGRAL is a separate id space that reuses the sourceTable
name and runs past 4,000, and ACCOUNT CANCELED is a transaction line type, not
an account state -- all 8 customers carrying it have current-year activity.

Recycling ships switched off (numid.recycleEmpty, default false). Every
reusable id still exists in Access DATGRAL, and a --sync run reassigns refs
with ON DUPLICATE KEY UPDATE customerId, so an id recycled before the utilities
cutover is silently handed back to its Access owner.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

apps/api/src/customers/customers.module.ts

@@ -1,9 +1,13 @@
 import { Module } from "@nestjs/common";
+import { SettingsModule } from "../settings/settings.module";
 import { CustomersController } from "./customers.controller";
 import { CustomersService } from "./customers.service";
+import { NumidService } from "./numid.service";
 
 @Module({
+  imports: [SettingsModule],
   controllers: [CustomersController],
-  providers: [CustomersService],
+  providers: [CustomersService, NumidService],
+  exports: [NumidService],
 })
 export class CustomersModule {}