Write a CONTRIBUTING.md guide for local Docker setup

[SHAURYASANYAL3]

🛑 The Problem

Open Source projects die without contributors, and contributors abandon projects if they can't get the app running locally within 10 minutes. Right now, setting up our Postgres database, Inngest server, and Next.js frontend is undocumented 'tribal knowledge'.

💡 The Solution

We need a comprehensive, copy-paste friendly CONTRIBUTING.md guide that holds the developer's hand from git clone to localhost:3000.

🛠️ Implementation Details

1. Create CONTRIBUTING.md in the root of the repository.
2. Write sections for:
   • Prerequisites (Node.js 18+, pnpm, Docker Desktop).
   • Installation (pnpm install).
   • Environment Variables (How to copy .env.example to .env).
   • Database Setup (How to run docker-compose up -d and pnpm db:push).
   • Running the App (pnpm dev).
3. Include a Troubleshooting section for common errors (e.g., port 5432 already in use).

✅ Acceptance Criteria

• The document is formatted beautifully with Markdown headers and code blocks.
• A developer following the guide line-by-line ends up with a working local environment.
• The guide is linked from the main README.md.

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Ready to tackle this? Comment .take below to get automatically assigned!

[sreerevanth]

@tapheret2