refactor: extract numbering logic into numbering.service.ts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/routes/admin/invoices.ts

@@ -4,7 +4,7 @@ import { requirePermission } from '../../middleware/auth';
 import { logAudit } from '../../services/audit';
 import { success, error, parseId } from '../../utils/response';
 import { parsePagination, buildPaginationMeta } from '../../utils/pagination';
-import { getNextNumber } from '../../utils/sequence';
+import { generateInvoiceNumber } from '../../services/numbering.service';
 import { parseBody } from '../../schemas/common';
 import { CreateInvoiceSchema, UpdateInvoiceSchema } from '../../schemas/invoices.schema';
 
@@ -106,7 +106,7 @@ export default async function invoicesRoutes(fastify: FastifyInstance): Promise<
     const prefix = `${yy}${typeCode}`;
 
     // Atomic numbering via number_sequences table
-    const nextNum = await getNextNumber('invoice', year);
+    const nextNum = await generateInvoiceNumber(year);
     const number = `${prefix}${String(nextNum).padStart(4, '0')}`;
     return success(reply, { number, next_number: number });
   });