Fix notification read state persistence across tabs

[belloaliyu11]

Overview

• Persist notification read state without allowing stale tabs to mark already-read notifications unread again.
• Merge stored read flags during hydration, local writes, setNotifications, and cross-tab storage events.
• Keep malformed or unavailable localStorage handling defensive and preserve timestamp revival for persisted notifications.

Related Issue
Closes #902

Changes

• Added monotonic read-state merging for persisted notification data.
• Added one global storage listener guarded against duplicate registration.
• Added focused Zustand store tests for persistence, malformed storage, retries/failures, stale writes, and cross-tab updates.

Verification Results

• PASS: corepack.cmd pnpm test -- app/state/__tests__/notifications.test.ts --runInBand
• PASS: corepack.cmd pnpm lint (existing warning in app/layout.tsx: @next/next/no-page-custom-font)
• PASS: git diff --check (only Git CRLF warning in working copy)
• FAIL: corepack.cmd pnpm type-check --pretty false due unrelated existing/sparse-checkout errors in app/layout.tsx, app/not-found.tsx, and app/state/walletPrefs.ts
• NOT RUN: prettier check because prettier is not installed in this repo

Acceptance Criteria

Criteria	Status	Notes
Read state persists safely	Met	Stored read flags are merged, not blindly replaced.
Cross-tab updates are safe	Met	Storage events apply read=true only and do not revert local reads.
Malformed/failed storage is defensive	Met	Invalid JSON and localStorage failures are ignored without breaking UI state.
Tests cover duplicate/boundary/failure behavior	Met	Focused Jest tests added for idempotency, malformed values, stale writes, and storage failures.

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