feat: automate access token generation via TOTP and PIN (#41, #24)

[SHIVANIUM-GIT]

This PR addresses the manual access token generation bottleneck by introducing a fully automated authentication flow. Instead of manually capturing the auth_code from a browser URL, this script handles the entire process—including TOTP generation and PIN verification—programmatically.

Fixes #41
Fixes #24

Changes Made

• New Automation Script: Added v3/python/login/automate_access_token.py which automates the login flow, OTP verification (via pyotp), and PIN entry to generate an access token.
• Environment Template: Added v3/python/.simple.env to provide a clear template for required credentials (client_id, secret_key, totp_key, etc.).
• Security Update: Updated .gitignore to ensure users don't accidentally commit their private .env files containing real credentials.
• Automatic Persistence: The script automatically saves the generated token back into the .env file for immediate use by other scripts.

How to Test

1. Rename .simple.env to .env and fill in your Fyers API credentials.
2. Run python v3/python/login/automate_access_token.py.
3. Verify that the access_token field in your .env is updated automatically without any manual browser interaction.