refactor(OUT-3896): use findFirst for expense lookup, simplify legacy match

- getExpenseByCopilotPaymentId now uses the relational query API
  (db.query.syncedPayments.findFirst) instead of a manual select + slice
- Register syncedPayments in the schema barrel so db.query knows it
- findLegacyExpenseByInvoice adopts the first match (only one fee exists
  per invoice, so multiple matches are duplicates of the same expense);
  warn when duplicates are present so they can be cleaned up

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: SandipBajracharya

src/db/schema/index.ts

@@ -2,6 +2,7 @@ import { settings } from './settings.schema'
 import { syncedContacts } from './syncedContacts.schema'
 import { syncedInvoices } from './syncedInvoices.schema'
 import { syncedItems } from './syncedItems.schema'
+import { syncedPayments } from './syncedPayments.schema'
 import { xeroConnectionStatus } from './xeroConnectionStatus.schema'
 import { xeroConnections } from './xeroConnections.schema'
 
@@ -12,4 +13,5 @@ export const schema = {
   syncedContacts,
   syncedInvoices,
   syncedItems,
+  syncedPayments,
 }

src/features/invoice-sync/lib/SyncedPayments.service.ts

@@ -42,18 +42,15 @@ class SyncedPaymentsService extends AuthenticatedXeroService {
   }
 
   async getExpenseByCopilotPaymentId(copilotPaymentId: string) {
-    const [result] = await this.db
-      .select()
-      .from(syncedPayments)
-      .where(
+    return await this.db.query.syncedPayments.findFirst({
+      where: (t, { and, eq }) =>
         and(
-          eq(syncedPayments.portalId, this.user.portalId),
-          eq(syncedPayments.tenantId, this.connection.tenantId),
-          eq(syncedPayments.copilotPaymentId, copilotPaymentId),
-          eq(syncedPayments.type, PaymentUserType.EXPENSE),
+          eq(t.portalId, this.user.portalId),
+          eq(t.tenantId, this.connection.tenantId),
+          eq(t.copilotPaymentId, copilotPaymentId),
+          eq(t.type, PaymentUserType.EXPENSE),
         ),
-      )
-    return result
+    })
   }
 
   async createPaymentRecord(

src/lib/xero/XeroAPI.ts

@@ -353,15 +353,13 @@ class XeroAPI {
         typeof tx.total === 'number' &&
         Math.round(tx.total * 100) === amountInCents,
     )
-    if (candidateTxns.length > 1) {
-      // Ambiguous: same-amount expenses on one invoice. Skip adopting and
-      // flag for manual cleanup of the legacy duplicates.
-      logger.warn(
-        'XeroAPI#findLegacyExpenseByInvoice :: Multiple legacy expenses match, not adopting',
-        { tenantId, invoiceReference, count: candidateTxns.length },
-      )
-      return undefined
-    }
+    if (candidateTxns.length > 1)
+      logger.warn('XeroAPI#findLegacyExpenseByInvoice :: Multiple legacy expenses match', {
+        tenantId,
+        invoiceReference,
+        count: candidateTxns.length,
+      })
+
     return candidateTxns[0]
   }