feat: add AccountsModule with list and QR endpoints

Implements GET /accounts (list all accounts) and GET /accounts/:id/qr
(returns QR code as base64 data URL) using the qrcode package.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/src/app.module.ts

@@ -5,6 +5,7 @@ import { HealthModule } from './modules/health/health.module';
 import { SearchModule } from './modules/search/search.module';
 import { GroupsModule } from './modules/groups/groups.module';
 import { RoutesModule } from './modules/routes/routes.module';
+import { AccountsModule } from './modules/accounts/accounts.module';
 
 @Module({
   imports: [
@@ -14,6 +15,7 @@ import { RoutesModule } from './modules/routes/routes.module';
     SearchModule,
     GroupsModule,
     RoutesModule,
+    AccountsModule,
   ],
 })
 export class AppModule {}