feat: add @account-kit/universal-account package with Particle Network integration

[soos3d]

Summary

Adds Universal Account integration for Account Kit, enabling chain abstraction with Particle Network. This allows users to have a single account, balance, and interaction point across all supported chains (EVM + Solana).

The Universal Account is automatically available via Alchemy's AccountKit. The AccountKit config and usage are unchanged.

Features

• Unified Balance: View and use assets across all chains as a single balance
• Cross-Chain Transactions: Send transactions to any chain without manual bridging
• Universal Gas: Pay gas fees with any supported token
• Solana Support: Interact with both EVM and Solana chains

Changes

New Package: @account-kit/universal-account

• UniversalAccountProvide(/aa-sdk/account-kit/universal-account/src/provider.tsx:81:0-198:1) - React context provider
• useUniversalAccount(/aa-sdk/account-kit/universal-account/src/provider.tsx:216:0-263:1) - Hook to initialize and manage Universal Account
• useUnifiedBalance(/aa-sdk/account-kit/universal-account/src/provider.tsx:265:0-342:1) - Hook to fetch unified balance across chains
• useSendTransaction(/aa-sdk/account-kit/universal-account/src/provider.tsx:352:0-551:1) - Hook for cross-chain transactions (transfer, buy, sell, convert)
• createUniversalAccountClient(/aa-sdk/account-kit/universal-account/src/client.ts:408:0-455:1) - Low-level client for non-React usage

Documentation

• Added Universal Accounts guide under Transactions section

Tests

• Unit tests for constants and client wrapper (21 tests)

Example

• Next.js demo app in examples/next-example/(/aa-sdk/account-kit/universal-account/examples/next-example:0:0-0:0)

Pull Request Checklist

• [✅ ] Did you add new tests and confirm existing tests pass? (yarn test)
• [ ✅] Did you update relevant docs? (docs are found in the site folder, and guidelines for updating/adding docs can be found in the contribution guide)
• [✅ ] Do your commits follow the Conventional Commits standard?
• [ ✅] Does your PR title also follow the Conventional Commits standard?
• [✅ ] If you have a breaking change, is it correctly reflected in your commit message? (e.g. feat!: breaking change)
• [✅ ] Did you run lint (yarn lint:check) and fix any issues? (yarn lint:write)
• [ ✅] Did you follow the contribution guidelines?

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PR-Codex overview

This PR introduces the @account-kit/universal-account package, enabling integration with Particle Network for chain abstraction. It includes configuration files, components, and demo examples for a seamless user experience across multiple blockchain networks.

Detailed summary

• Added favicon.ico, SVG icons, and configuration files for the demo app.
• Implemented postcss.config.mjs and next.config.ts for Tailwind CSS and Next.js setup.
• Created vitest.config.ts for testing configurations.
• Developed a README.md for the demo app, detailing setup and usage.
• Introduced various TypeScript configuration files for type safety.
• Implemented components and hooks in the demo app for user authentication, unified balances, and transaction handling.
• Added tests for the UniversalAccountClient to ensure functionality and correct parameter passing.
• Updated documentation for third-party integration with Universal Accounts, including installation and usage instructions.

The following files were skipped due to too many changes: account-kit/universal-account/src/__tests__/client.test.ts, account-kit/universal-account/examples/next-example/app/components/UniversalAccountDemo.tsx, account-kit/universal-account/src/client.ts, account-kit/universal-account/src/provider.tsx, yarn.lock, account-kit/universal-account/README.md

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