fix: resolve backend property mismatches and implement balance reversal

- fix(backend): correct activity controller to use 'sub' instead of 'id' from JWT
- fix(backend): implement automatic balance reversal when an expense is deleted
- fix(backend): fix expense calculator bug affecting participants who paid more than they owed
- fix(backend): add validation to ensure total payments match the expense amount
- fix(mobile): update SkeletonList colors to properly support dark mode
- chore: update .gitignore to exclude .expo, build artifacts, and logs

Author: Arun-kushwaha007

.gitignore

@@ -10,6 +10,18 @@ coverage
 .agents
 .agent
 .turbo
+.expo
+node_modules
+dist
+.next
+.next/
+out/
+build/
+*.tsbuildinfo
+*.log
+.DS_Store
+.idea
+.vscode
 skills-lock.json
 *.pem
 *.key

apps/backend/.turbo/turbo-test.log

@@ -2,27 +2,47 @@
 > backend@1.0.0 test D:\ak\project\FairShare\apps\backend
 > jest --runInBand --passWithNoTests
 
-PASS src/settlements/settlements.integration.spec.ts (30.803 s)
-(node:22644) NOTE: The AWS SDK for JavaScript (v2) has reached end-of-support.
-It will no longer receive updates or releases.
-
-Please migrate your code to use AWS SDK for JavaScript (v3).
-For more information, check the blog post at https://a.co/cUPnyil
-(Use `node --trace-warnings ...` to show where the warning was created)
-PASS src/receipts/receipts.service.spec.ts
+PASS src/receipts/receipts.integration.spec.ts (27.096 s)
+PASS src/payments/payments.service.spec.ts
+[Nest] 27236  - 03/25/2026, 11:37:32 PM     LOG [PaymentsService] Payment succeeded and settlement recorded paymentId=payment-1
+[Nest] 27236  - 03/25/2026, 11:37:32 PM     LOG [PaymentsService] Payment succeeded and settlement recorded paymentId=payment-1
+[Nest] 27236  - 03/25/2026, 11:37:32 PM     LOG [PaymentsService] Payment succeeded and settlement recorded paymentId=payment-1
 PASS src/expenses/expenses.integration.spec.ts
+PASS src/groups/groups.service.spec.ts
 PASS src/expenses/expenses.service.spec.ts
 PASS src/settlements/settlements.service.spec.ts
-PASS src/groups/groups.service.spec.ts
+PASS src/settlements/settlements.integration.spec.ts
+[Nest] 27236  - 03/25/2026, 11:37:42 PM   ERROR [NotificationsService] Expo push send failed
+Error: transient failure
+    at Object.<anonymous> (D:\ak\project\FairShare\apps\backend\src\notifications\notifications.service.spec.ts:98:30)
+    at Promise.then.completed (D:\ak\project\FairShare\node_modules\.pnpm\jest-circus@29.7.0\node_modules\jest-circus\build\utils.js:298:28)
+    at new Promise (<anonymous>)
+    at callAsyncCircusFn (D:\ak\project\FairShare\node_modules\.pnpm\jest-circus@29.7.0\node_modules\jest-circus\build\utils.js:231:10)
+    at _callCircusTest (D:\ak\project\FairShare\node_modules\.pnpm\jest-circus@29.7.0\node_modules\jest-circus\build\run.js:316:40)
+    at runNextTicks (node:internal/process/task_queues:64:5)
+    at processImmediate (node:internal/timers:472:9)
+    at async _runTest (D:\ak\project\FairShare\node_modules\.pnpm\jest-circus@29.7.0\node_modules\jest-circus\build\run.js:252:3)
+    at async _runTestsForDescribeBlock (D:\ak\project\FairShare\node_modules\.pnpm\jest-circus@29.7.0\node_modules\jest-circus\build\run.js:126:9)
+    at async _runTestsForDescribeBlock (D:\ak\project\FairShare\node_modules\.pnpm\jest-circus@29.7.0\node_modules\jest-circus\build\run.js:121:9)
+    at async run (D:\ak\project\FairShare\node_modules\.pnpm\jest-circus@29.7.0\node_modules\jest-circus\build\run.js:71:3)
+    at async runAndTransformResultsToJestFormat (D:\ak\project\FairShare\node_modules\.pnpm\jest-circus@29.7.0\node_modules\jest-circus\build\legacy-code-todo-rewrite\jestAdapterInit.js:122:21)
+    at async jestAdapter (D:\ak\project\FairShare\node_modules\.pnpm\jest-circus@29.7.0\node_modules\jest-circus\build\legacy-code-todo-rewrite\jestAdapter.js:79:19)
+    at async runTestInternal (D:\ak\project\FairShare\node_modules\.pnpm\jest-runner@29.7.0\node_modules\jest-runner\build\runTest.js:367:16)
+    at async runTest (D:\ak\project\FairShare\node_modules\.pnpm\jest-runner@29.7.0\node_modules\jest-runner\build\runTest.js:444:34)
 PASS src/notifications/notifications.service.spec.ts
+[Nest] 27236  - 03/25/2026, 11:37:42 PM     LOG [NotificationsService] {"event":"notification_event_queued","channel":"fairshare:notifications","payload":{"userIds":["user-1"],"payload":{"type":"expense_created","title":"Expense added","body":"Dinner was added"},"queuedAt":"2026-03-25T18:07:42.461Z"}}
+[Nest] 27236  - 03/25/2026, 11:37:42 PM    WARN [NotificationsService] {"event":"notification_invalid_tokens_removed","count":1}
+[Nest] 27236  - 03/25/2026, 11:37:42 PM     LOG [NotificationsService] {"event":"notification_push_sent","ticketCount":2}
+[Nest] 27236  - 03/25/2026, 11:37:42 PM     LOG [NotificationsService] {"event":"notification_push_sent","ticketCount":1}
 PASS src/balances/balances.service.spec.ts
 PASS src/users/users.service.spec.ts
 PASS src/simplify/simplify.service.spec.ts
+PASS src/receipts/receipts.service.spec.ts
 PASS src/activity/activity.service.spec.ts
 PASS src/expenses/expense-calculator.spec.ts
 
-Test Suites: 12 passed, 12 total
-Tests:       16 passed, 16 total
+Test Suites: 14 passed, 14 total
+Tests:       30 passed, 30 total
 Snapshots:   0 total
-Time:        38.565 s
+Time:        45.038 s
 Ran all test suites.

apps/backend/src/activity/activity.controller.ts

@@ -1,5 +1,7 @@
-import { Controller, Get, Param, Query, UseGuards, Request } from '@nestjs/common';
+import { Controller, Get, Param, Query, UseGuards } from '@nestjs/common';
 import { JwtAuthGuard } from '../auth/guards/jwt-auth.guard';
+import { CurrentUser } from '../common/decorators/current-user.decorator';
+import { JwtPayload } from '../auth/types/auth.types';
 import { ActivityService } from './activity.service';
 
 @Controller('activity')
@@ -8,8 +10,8 @@ export class ActivityController {
   constructor(private readonly activityService: ActivityService) {}
 
   @Get()
-  getUserActivity(@Request() req: any, @Query('cursor') cursor = '0', @Query('limit') limit = '20') {
-    return this.activityService.getUserActivity(req.user.id, Number(cursor), Number(limit));
+  getUserActivity(@CurrentUser() user: JwtPayload, @Query('cursor') cursor = '0', @Query('limit') limit = '20') {
+    return this.activityService.getUserActivity(user.sub, Number(cursor), Number(limit));
   }
 
   @Get('group/:id')

apps/backend/src/expenses/expense-calculator.ts

@@ -1,4 +1,4 @@
-import { CreateExpenseSplitInputDto } from './dto/create-expense.dto';
+import { CreateExpenseSplitInputDto } from './dto/create-expense.dto';
 
 export interface BalanceDelta {
   userId: string;
@@ -18,7 +18,7 @@ export const calculateBalanceDeltas = (payerId: string, splits: CreateExpenseSpl
     const paid = BigInt(split.paidAmountCents);
     const net = owed - paid;
 
-    if (net > 0n) {
+    if (net !== 0n) {
       deltas.push({
         userId: split.userId,
         counterpartyUserId: payerId,

apps/backend/src/expenses/expenses.service.ts

@@ -36,10 +36,12 @@ export class ExpensesService {
     }
 
     const owedSum = sumMoney(dto.splits.map((split) => split.owedAmountCents));
+    const paidSum = sumMoney(dto.splits.map((split) => split.paidAmountCents));
     try {
-      assertMoneyEquality(owedSum, totalAmount, 'Split sum must equal total amount');
-    } catch {
-      throw new BadRequestException('Split sum must equal total amount');
+      assertMoneyEquality(owedSum, totalAmount, 'Total owed sum must equal total amount');
+      assertMoneyEquality(paidSum, totalAmount, 'Total paid sum must equal total amount');
+    } catch (e: any) {
+      throw new BadRequestException(e.message);
     }
 
     if (idempotencyKey) {
@@ -230,12 +232,34 @@ export class ExpensesService {
   }
 
   async remove(id: string, actorUserId: string): Promise<{ success: true }> {
-    const expense = await this.prisma.expense.findUnique({ where: { id } });
+    const expense = await this.prisma.expense.findUnique({
+      where: { id },
+      include: { splits: true },
+    });
     if (!expense) {
       throw new NotFoundException('Expense not found');
     }
 
     await this.prisma.$transaction(async (tx) => {
+      const deltas = calculateBalanceDeltas(
+        expense.payerId,
+        expense.splits.map((s) => ({
+          userId: s.userId,
+          owedAmountCents: s.owedAmountCents.toString(),
+          paidAmountCents: s.paidAmountCents.toString(),
+        })),
+      );
+
+      for (const delta of deltas) {
+        await this.balancesService.adjustBalance(
+          tx as unknown as Prisma.TransactionClient,
+          expense.groupId,
+          delta.userId,
+          delta.counterpartyUserId,
+          -delta.delta,
+        );
+      }
+
       await tx.split.deleteMany({ where: { expenseId: id } });
       await tx.expense.delete({ where: { id } });
       await tx.activity.create({