Feat/local setup doc

[egwujiohaifesinachiperpetual-max]

Closes #296
This pull request updates the CONTRIBUTING.md file to include complete, step-by-step instructions for setting up the project locally from scratch. Prior to this, the document focused solely on the blueprint contribution workflow, leaving the local setup and first-run experience undocumented.

Changes

• Development Setup Guide: Added detailed steps for cloning the repository and running npm install.
• Environment Variables: Instructed copying .env.example to .env and documented the minimum required variables for testnet local development.
• Optional Services: Noted that PostgreSQL and Redis are optional when using the mock data path, and detailed how to set up PostgreSQL (running migrations with npm run db:migrate and seeding test data with npm run db:seed) if needed.
• Dev Servers: Documented starting the development server for the basic dashboard (npm run dev) and optionally the full WebSocket server (npm run dev:ws).

Verification Done

• Verified that all paths and commands align with the scripts configured in package.json and the structure of .env.example.
• Verified formatting is correct markdown.