docs: document Windows setup fix for prisma .env symlink error

[khushal-winner]

What does this PR do?

This PR documents a Windows-specific issue affecting packages/prisma/.env during local development setup.

On Windows, the file may be created as a Unix-style symlink pointing to ../../.env. This can cause the following error:

unexpected character "/" in variable name "../../.env"

The README now includes:

• Explanation of why the issue happens on Windows
• Command-line fix (Git Bash / WSL)
• Manual fix (File Explorer method)

This PR only updates documentation and does not modify any application code.

Tested on

• Windows 11
• Git Bash
• Docker Desktop

Visual Demo (For contributors especially)

A visual demonstration is strongly recommended, for both the original and new change (video / image - any one).

Video Demo (if applicable):

• Show screen recordings of the issue or feature.
• Demonstrate how to reproduce the issue, the behavior before and after the change.

Image Demo (if applicable):

• failed setup proof before fix

• after fix

Mandatory Tasks (DO NOT REMOVE)

• [✔] I have self-reviewed the code.
• [✔] I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. N/A – this PR only updates README.md.
• [✔] I confirm automated tests are in place that prove my fix is effective or that my feature works. N/A – documentation-only change.

How should this be tested?

1. Follow the local setup instructions on Windows.

2. Allow packages/prisma/.env to be created as a symlink.

3. Run yarn dx

4. Observe the error:

   unexpected character "/" in variable name "../../.env"

5. Apply the documented fix (remove the symlink and copy the root .env file).

6. Re-run yarn dx.

Expected result:

• The error no longer occurs.
• Prisma setup and Docker database initialization succeed.

---

[CLAassistant]

All committers have signed the CLA.

[cubic-dev-ai]

No issues found across 2 files

[sahitya-chandra]

I have also seen contributors using Windows facing this issue while locally setting up.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 1 additional finding.