Clear npm dependency vulnerabilities

[ramtamilselvan]

Summary:

• Clears npm audit findings across the audited npm workspaces.
• Migrates contracts tooling to the Hardhat 3 stack and refreshes docs dependencies.
• Keeps this branch scoped to dependency security cleanup only.

Validation:

• npm audit --audit-level=low across npm lockfile workspaces
• npm run build in docs/site
• npx hardhat build --no-typechain
• npx hardhat test test/*.test.ts --no-compile