dify - 💡(How to fix) Fix [Refactor/Chore] Update local setup for split Docker middleware env files [1 pull requests]

Self Checks

• I have read the Contributing Guide and Language Policy.
• This is only for refactors or chores; if you would like to ask a question, please head to Discussions.
• I have searched for existing issues search for existing issues, including closed ones.
• I confirm that I am using English to submit this report, otherwise it will be closed.
• Please do not modify this template :) and fill in all the required fields.

Description

The Docker env layout now stores the middleware template at docker/envs/middleware.env.example, while some local setup paths still refer to the old docker/middleware.env.example location. The development cleanup target also does not cover all middleware data directories produced by the current middleware compose stack.

Motivation

Local setup commands should create docker/middleware.env from the current template path after the Docker env split. Cleanup should be repeatable even when the generated env file is absent and should remove data for the middleware services currently managed by docker-compose.middleware.yaml.

Additional Context

This affects local developer setup and maintenance scripts, including make prepare-docker, make dev-clean, dev/setup, and dev/pytest/pytest_full.sh.