fix: improve local development stability and pnpm compatibility

[johnnylemonny]

This PR addresses several issues encountered during local development across different terminal environments and modernizes the package management infrastructure.

Changes:

• pnpm Migration: Introduced pnpm-workspace.yaml and optimized dependencies for better workspace support and faster installs.
• Environment Handling: Resolved issues with cross-env where environment variables were not consistently passed in certain PowerShell/Bash setups.
• Dependency Update: Updated package-build-stats to version 8.2.7 to benefit from the latest build logic fixes and stability improvements.

Motivation

To ensure that new contributors can set up the project seamlessly regardless of their OS or terminal of choice, and to move towards a more robust monorepo-ready infrastructure.

Testing

• Verified pnpm install and pnpm run dev on both Windows (PowerShell) and Linux environments.
• Confirmed that build service endpoints are correctly picked up from .env.