feat: Update musd calculator (MetaMask#27949)

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## **Description**

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also include relevant motivation and context. Have in mind the following
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1. What is the reason for the change?
2. What is the improvement/solution?
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This PR provides some minor fixes and improvements to the mUSD
calculator:

- Guard against / set default value for a variable
- Use swap navigation instead of deeplink for reduced friction
- Move the disclaimer to the bottom of the page content

## **Changelog**

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CHANGELOG entry: null

## **Related issues**

Fixes: n/a

## **Manual testing steps**

```gherkin
Feature: my feature name

  Scenario: user [verb for user action]
    Given [describe expected initial app state]

    When user [verb for user action]
    Then [describe expected outcome]
```

## **Screenshots/Recordings**

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### **Before**

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### **After**

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src="https://github.com/user-attachments/assets/918eeaf3-0f22-41fb-aabc-a96013925e08"
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## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
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Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Medium risk because it changes the mUSD swap action from a deeplink to
in-app swap navigation and adjusts rewards state rehydration/selectors
to tolerate missing campaign status data, which could affect routing and
campaign UI behavior if misconfigured.
> 
> **Overview**
> Updates the mUSD calculator header to use a new localized
`rewards.musd.page_title` string and tweaks layout by moving the
disclaimer to the bottom with updated styling.
> 
> Replaces the Swap button’s deeplink (`link.metamask.io/swap`) with
in-app swap navigation via `useSwapBridgeNavigation`, preconfiguring
ETH→mUSD tokens, and updates tests accordingly.
> 
> Hardens Rewards redux state handling by defaulting
`campaignParticipantStatuses` to `{}` on rehydrate and making related
selectors null-safe, preventing crashes when the field is missing from
persisted payloads.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
fc1814e. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: Montoya

app/components/UI/Rewards/Views/MusdCalculatorView.tsx

@@ -18,7 +18,7 @@ const MusdCalculatorView: React.FC = () => {
         style={tw.style('flex-1 bg-default')}
       >
         <HeaderCompactStandard
-          title={strings('rewards.musd.title')}
+          title={strings('rewards.musd.page_title')}
           onBack={() => navigation.goBack()}
         />
         <MusdCalculatorTab />

app/components/UI/Rewards/components/Tabs/MusdCalculatorTab/MusdCalculatorTab.test.tsx

@@ -2,8 +2,11 @@ import React from 'react';
 import { render, fireEvent, waitFor } from '@testing-library/react-native';
 import MusdCalculatorTab from './MusdCalculatorTab';
 
+const mockGoToSwaps = jest.fn();
+
 jest.mock('react-redux', () => ({
   useSelector: jest.fn(() => 'usd'),
+  useDispatch: jest.fn(() => jest.fn()),
 }));
 
 jest.mock('../../../../../../../locales/i18n', () => ({
@@ -14,6 +17,11 @@ jest.mock('../../../../../../core/DeeplinkManager', () => ({
   handleDeeplink: jest.fn(),
 }));
 
+jest.mock('../../../../Bridge/hooks/useSwapBridgeNavigation', () => ({
+  useSwapBridgeNavigation: () => ({ goToSwaps: mockGoToSwaps }),
+  SwapBridgeNavigationLocation: { Rewards: 'Rewards' },
+}));
+
 jest.mock('../../../../../../util/theme', () => {
   const { mockTheme } = jest.requireActual('../../../../../../util/theme');
   return {
@@ -54,17 +62,11 @@ describe('MusdCalculatorTab', () => {
     });
   });
 
-  it('calls handleDeeplink with swap URL when Swap button is pressed', () => {
-    const { handleDeeplink } = jest.requireMock(
-      '../../../../../../core/DeeplinkManager',
-    );
-
+  it('navigates to swap screen when Swap button is pressed', () => {
     const { getByText } = render(<MusdCalculatorTab />);
     fireEvent.press(getByText('rewards.musd.swap_button'));
 
-    expect(handleDeeplink).toHaveBeenCalledWith({
-      uri: expect.stringContaining('link.metamask.io/swap'),
-    });
+    expect(mockGoToSwaps).toHaveBeenCalled();
   });
 
   it('updates input value when amount changes', () => {

app/components/UI/Rewards/components/Tabs/MusdCalculatorTab/MusdCalculatorTab.tsx

@@ -2,10 +2,8 @@ import React, { useCallback, useMemo, useState } from 'react';
 import { ScrollView } from 'react-native';
 import {
   Box,
-  Icon,
-  IconName,
-  IconSize,
   Text,
+  TextColor,
   TextVariant,
   Button,
   ButtonVariant,
@@ -18,17 +16,40 @@ import { KeyValueRowStubs } from '../../../../../../component-library/components
 import { handleDeeplink } from '../../../../../../core/DeeplinkManager';
 import useFiatFormatter from '../../../../SimulationDetails/FiatDisplay/useFiatFormatter';
 import { BigNumber } from 'bignumber.js';
+import { EthScope } from '@metamask/keyring-api';
+import Routes from '../../../../../../constants/navigation/Routes';
+import {
+  SwapBridgeNavigationLocation,
+  useSwapBridgeNavigation,
+} from '../../../../Bridge/hooks/useSwapBridgeNavigation';
+import { BridgeToken } from '../../../../Bridge/types';
+import {
+  MUSD_TOKEN,
+  MUSD_TOKEN_ADDRESS,
+} from '../../../../Earn/constants/musd';
+import { getNativeSourceToken } from '../../../../Bridge/utils/tokenUtils';
 
 const ANNUAL_BONUS_RATE = 0.03;
 const BUY_MUSD_URL =
   'https://link.metamask.io/buy?address=0xaca92e438df0b2401ff60da7e4337b687a2435da&amount=100&chainid=1&sig_params=address%2Camount%2Cchainid%2Cutm_source&utm_source=rewards&sig=SdHOoh_QvT1bs8B6g-qCyLH5mUEczYzeOfAv9SNRm4CKjR6uBnUp4e1-Vcojb39fWWScBrui2GLftNlJKQlrAQ';
-const SWAP_MUSD_URL =
-  'https://link.metamask.io/swap?from=eip155%3A1%2Fslip44%3A60&sig_params=from%2Cto%2Cutm_source&to=eip155%3A1%2Ferc20%3A0xacA92E438df0B2401fF60dA7E4337B687a2435DA&utm_source=rewards&sig=mCsMuZB-omwEg9WvGOwA8nuc8NvXj7uFfC_Pn-6Nmwlce2GF356tbZbHIgzYHWhmLb4kvUKMTpj4eb0yUrle1Q';
+
+const MUSD_DEST_TOKEN: BridgeToken = {
+  address: MUSD_TOKEN_ADDRESS,
+  symbol: MUSD_TOKEN.symbol,
+  name: MUSD_TOKEN.name,
+  decimals: MUSD_TOKEN.decimals,
+  chainId: '0x1',
+};
 
 const MusdCalculatorTab: React.FC = () => {
   const tw = useTailwind();
   const [musdAmount, setMusdAmount] = useState('1000');
 
+  const ethSourceToken = useMemo(
+    () => getNativeSourceToken(EthScope.Mainnet),
+    [],
+  );
+
   const musdCalculations = useMemo(() => {
     const amount = parseFloat(musdAmount) || 0;
     const annualizedBonus = amount * ANNUAL_BONUS_RATE;
@@ -59,9 +80,16 @@ const MusdCalculatorTab: React.FC = () => {
     handleDeeplink({ uri: BUY_MUSD_URL });
   }, []);
 
+  const { goToSwaps } = useSwapBridgeNavigation({
+    location: SwapBridgeNavigationLocation.Rewards,
+    sourcePage: Routes.REWARDS_DASHBOARD,
+    sourceToken: ethSourceToken,
+    destToken: MUSD_DEST_TOKEN,
+  });
+
   const handleSwapMusd = useCallback(() => {
-    handleDeeplink({ uri: SWAP_MUSD_URL });
-  }, []);
+    goToSwaps();
+  }, [goToSwaps]);
 
   return (
     <ScrollView
@@ -132,14 +160,6 @@ const MusdCalculatorTab: React.FC = () => {
         </Box>
       </Box>
 
-      {/* Disclaimer */}
-      <Box twClassName="flex-row gap-2 items-center">
-        <Icon name={IconName.Info} size={IconSize.Sm} />
-        <Text variant={TextVariant.BodySm} twClassName="flex-1">
-          {strings('rewards.musd.disclaimer')}
-        </Text>
-      </Box>
-
       {/* Action Buttons */}
       <Box twClassName="gap-3">
         <Button
@@ -159,6 +179,15 @@ const MusdCalculatorTab: React.FC = () => {
           {strings('rewards.musd.swap_button')}
         </Button>
       </Box>
+
+      {/* Disclaimer */}
+      <Text
+        variant={TextVariant.BodySm}
+        color={TextColor.TextAlternative}
+        twClassName="text-center"
+      >
+        {strings('rewards.musd.disclaimer')}
+      </Text>
     </ScrollView>
   );
 };

app/reducers/rewards/index.ts

@@ -688,7 +688,7 @@ const rewardsSlice = createSlice({
               unlockedRewards: action.payload.rewards.unlockedRewards,
               campaigns: action.payload.rewards.campaigns,
               campaignParticipantStatuses:
-                action.payload.rewards.campaignParticipantStatuses,
+                action.payload.rewards.campaignParticipantStatuses ?? {},
               ondoCampaignLeaderboardPositions:
                 action.payload.rewards.ondoCampaignLeaderboardPositions ?? {},
               hideUnlinkedAccountsBanner:

app/reducers/rewards/selectors.ts

@@ -172,13 +172,13 @@ export const selectCampaignParticipantStatuses = (state: RootState) =>
 export const selectCampaignParticipantStatusById =
   (campaignId: string | undefined) => (state: RootState) =>
     campaignId
-      ? (state.rewards.campaignParticipantStatuses[campaignId] ?? null)
+      ? (state.rewards.campaignParticipantStatuses?.[campaignId] ?? null)
       : null;
 
 export const selectCampaignParticipantCount =
   (campaignId: string | undefined) => (state: RootState) =>
     campaignId
-      ? (state.rewards.campaignParticipantStatuses[campaignId]
+      ? (state.rewards.campaignParticipantStatuses?.[campaignId]
           ?.participantCount ?? null)
       : null;
 

locales/languages/de.json

@@ -7872,6 +7872,7 @@
     "active_boosts_title": "Aktive Boosts",
     "season_1": "Saison 1",
     "musd": {
+      "page_title": "mUSD",
       "title": "mUSD-Bonus-Rechner",
       "description": "Finden Sie heraus, wie viel Sie durch die Konvertierung Ihrer Stablecoins in mUSD verdienen können.",
       "amount_label": "Konvertierter Betrag",

locales/languages/el.json

@@ -7872,6 +7872,7 @@
     "active_boosts_title": "Ενεργές ενισχύσεις",
     "season_1": "Περίοδος 1",
     "musd": {
+      "page_title": "mUSD",
       "title": "Εκτίμηση του μπόνους σε mUSD",
       "description": "Δείτε πόσα μπορείτε να κερδίσετε μετατρέποντας τα stablecoins σας σε mUSD.",
       "amount_label": "Το ποσό μετατράπηκε",

locales/languages/en.json

@@ -7878,6 +7878,7 @@
     "active_boosts_title": "Active boosts",
     "season_1": "Season 1",
     "musd": {
+      "page_title": "mUSD",
       "title": "mUSD bonus calculator",
       "description": "See how much you could earn by converting your stablecoins to mUSD.",
       "amount_label": "Amount converted",

locales/languages/es.json

@@ -7872,6 +7872,7 @@
     "active_boosts_title": "Potenciadores activos",
     "season_1": "Temporada 1",
     "musd": {
+      "page_title": "mUSD",
       "title": "Calculadora del bono en mUSD",
       "description": "Descubre cuánto podrías ganar al convertir tus monedas estables a mUSD.",
       "amount_label": "Monto convertido",

locales/languages/fr.json

@@ -7872,6 +7872,7 @@
     "active_boosts_title": "Boosts actifs",
     "season_1": "Saison 1",
     "musd": {
+      "page_title": "mUSD",
       "title": "Calculateur du bonus en mUSD",
       "description": "Découvrez combien vous pourriez gagner en convertissant vos stablecoins en mUSD.",
       "amount_label": "Montant converti",