feat(authenticated-user-storage): add watchlist support

[Prithpal-Sooriya]

Explanation

https://consensyssoftware.atlassian.net/browse/ASSETS-3219

Add watchlist support to the AUS SDK.

References

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Medium Risk
Adds a new persisted user-data domain with new network requests, caching, and runtime validation; risk is mainly around API contract/validation mismatches and cache invalidation behavior.

Overview
Adds assets watchlist support to the authenticated-user-storage SDK via new getAssetsWatchlist (returns null on 404) and setAssetsWatchlist methods plus corresponding messenger actions.

Introduces an AssetsWatchlistBlob schema/type and exports ASSETS_WATCHLIST_MAX_ASSETS (100), enforcing the cap on writes via superstruct while keeping reads lenient. Updates tests/fixtures/mocks to cover headers, error handling, caching, and invalidation, and refreshes README/CHANGELOG to document the new domain.

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