Description

Adds custom toast notifications for the mUSD Merkl rewards claiming flow. When a user initiates a Merkl claim transaction, the toast tracks the transaction lifecycle: in-progress (with spinner) → success/failed (auto-hides after 5s).

Also fixes a pre-existing bug in home.component.js where the "network added" notification would reappear after navigating away and back — onAutoHide was calling the raw setEditedNetwork() action creator (no-op) instead of the dispatched clearEditedNetwork() prop.

Changes:

• useMerklClaimStatus hook — monitors Redux transactions for Merkl Distributor address, detects pending → confirmed/failed/dropped transitions, and exposes toastState + dismissToast
• MerklClaimToast component in ToastMaster — renders loading spinner (in-progress), checkmark (success), or error icon (failed) using @metamask/design-system-react icons
• 3 new i18n strings for toast messages
• Bug fix: home.component.js onAutoHide now calls clearEditedNetwork() (dispatched) instead of setEditedNetwork() (undispatched import)

Note: This has been tested together with the full claim-musd branch changes from PR #39901 (Merkl rewards functionality — still WIP), but this PR is independent and can be merged first.

Changelog

CHANGELOG entry: Added toast notifications for mUSD reward claim transaction status (in-progress, success, failed); fixed a bug where the "network added" home notification would reappear after navigation

Related issues

Fixes: https://consensyssoftware.atlassian.net/browse/MUSD-303

Manual testing steps

1. Apply the full Merkl claiming changes from the claim-musd branch (PR feat: add Merkl rewards functionality and localization #39901) on top of this branch
2. Hold mUSD with unclaimed Merkl rewards, claim via the Claim flow
3. Verify the "Your mUSD bonus is processing" toast appears with a spinning loader
4. After transaction confirms, verify "Your mUSD bonus is here!" toast appears with a checkmark and auto-hides after 5 seconds
5. Reject a claim transaction — verify "Bonus claim failed" toast appears with an error icon
6. For the bug fix: add a custom network, wait for the "successfully added" notification to auto-hide, navigate away and back — verify it does NOT reappear

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.