[Good First Issue]: Improve .env.example documentation

[youngcoder45]

Summary

Explain environment variables in .env.example.

Context

New contributors may not know what each variable does.

Scope (what's in / out)

Files:

• .env.example

Acceptance criteria

• Each variable has explanation
• Beginner-friendly comments

Suggested approach / hints

1. Open .env.example
2. Add comments explaining each variable

Estimated difficulty

XS (≤ 1 hour)

Maintainer checklist

• Task is well-scoped and actionable
• Has clear acceptance criteria
• Includes pointers to relevant code/docs
• Does not require private credentials/tokens