docs: improve onboarding and local setup guide

[Deepiga0706]

Pull Request Overview

This Pull Request improves the onboarding experience for first-time contributors by enhancing the project documentation and setup instructions.

The changes address gaps in the local development guide by documenting required environment variables, providing a sample .env.example file, adding platform-specific setup commands, and including troubleshooting guidance for common setup issues. These improvements make it easier for new contributors to configure and run the project locally without additional assistance.

Related Issues

• Resolves docs: improve environment setup documentation for local development #7

Architecture and Implementation Details

• Added a .env.example file containing default local development environment variables.
• Added an Environment Setup section to the README with instructions for Linux/macOS, Windows CMD, and Windows PowerShell.
• Documented required environment variables and their default local values.
• Added a Troubleshooting section covering common setup issues such as Docker availability, port conflicts, and missing pnpm installations.
• Improved onboarding documentation to streamline local project setup for new contributors.

Breaking Changes

• Yes (Describe below)
• No

Testing Methodology

1. Reviewed all setup instructions for accuracy and consistency.
2. Verified that documented commands are valid for Linux/macOS and Windows environments.
3. Confirmed environment variables listed in the README match the provided .env.example file.
4. Validated Markdown formatting and documentation structure.

Performance & Observability Impact

This Pull Request introduces documentation-only changes and does not affect runtime performance, telemetry collection, observability pipelines, infrastructure behavior, or application functionality.

Contributor Checklist

• I have read and adhered to the PulseStack Contributing Guidelines.
• I have successfully executed the local test suite without errors.
• I have updated the corresponding documentation to reflect these changes.
• I have added adequate test coverage for my implementation.
• I have verified that my code aligns with the repository's formatting and linting standards.