Add *.env to gitignore (#2106)

# Description

Added *.env to template .gitignore file, so that backup_{x}.env files
created by subsequent cdf auth init commands are not accidently picked
up by Cursor.

## Changelog

- [x] Patch
- [ ] Skip

## cdf

### Added

- When running `cdf repo init`, `*.env` is included in the `.gitignore`
template

## templates

No changes.

