fix: update CI workflows to use corepack and install dependencies with frozen lockfile

[rube-de]

This pull request streamlines the GitHub Actions workflows, updates dependencies, and introduces a new package.json file for the project. The most notable changes include simplifying the setup of pnpm and caching, updating the viem dependency to a more flexible version range, and adding a package.json file with project metadata and configuration.

Reproducible Builds:

• all workflows use now pnpm install --frozen-lockfile
• all workflows use now the package manger from root package.json via pnpm/action-setup@v4

Workflow Simplifications:

• Replaced the manual setup of pnpm and caching in all workflows (ci-docs, ci-lint, ci-playwright, ci-test, contracts-test, publish) with the cache: 'pnpm' option in actions/setup-node@v4 for improved maintainability. Also removed redundant steps like pnpm store path and actions/cache. [1] [2] [3] [4] [5] [6] [7]

Dependency Updates:

• Updated the viem dependency in examples/wagmi-v2/package.json and integrations/viem-v2/package.json to use the 2.x version range instead of a specific version, allowing for minor version updates without manual intervention. [1] [2]

Project Configuration:

• Added a new package.json file at the root of the project with metadata, Node.js version requirements (>=18.0.0), and pnpm configuration, including an override for the elliptic package.
• Removed the elliptic override from pnpm-workspace.yaml, as it is now managed in the new package.json.

[netlify]

✅ Deploy Preview for oasisprotocol-sapphire-paratime canceled.

Name	Link
🔨 Latest commit	af64a34
🔍 Latest deploy log	https://app.netlify.com/sites/oasisprotocol-sapphire-paratime/deploys/680907609e189c0008eea586

[netlify]

✅ Deploy Preview for oasisprotocol-sapphire-paratime canceled.

Name	Link
🔨 Latest commit	4579ce1
🔍 Latest deploy log	https://app.netlify.com/sites/oasisprotocol-sapphire-paratime/deploys/680fc8ff91e54000083764b9