migrate website to Poetry and simplify arch.

[DocArmoryTech]

Consolidates the website/ app around Poetry, a single main.py entrypoint, and .env-based configuration. Adds systemd service templates and log rotation.

BREAKING CHANGE: configuration moved from conf/config.py and config.cfg* to .env.

Dependency management

• Replace requirements.txt with pyproject.toml and Poetry; add poetry.lock.
• Define CLI commands via main.py: --dev, --db-init, --db-migrate, --db-upgrade, --db-downgrade.

Application architecture

• Consolidate app_creation.py, launch.py, and migrate.py into a single website/main.py.
• Provide a module-level WSGI app (main:app) so Gunicorn can run the site.
• Keep Flask DB operations available via CLI; initialization performed in --db-init.

Configuration

• Load settings from .env in app/__init__.py (e.g., DATABASE_URI, SECRET_KEY, FLASK_URL, FLASK_PORT, MISP_MODULE, SESSION_*).
• Remove FLASK_ENV; development is explicit via --dev.

Utilities

• Refactor app/utils/utils.py to cache env vars (MISP_MODULE, QUERIES_LIMIT, ADMIN_PASSWORD).
• Replace ADMIN_USER with ADMIN_PASSWORD presence; in dev, auto-generate if missing; in prod, warn if absent.
• Remove file-based storage (admin_password.txt, config.cfg).

Linting and formatting

• Add website/.flake8 and configure flake8.
• Configure Black and isort in website/pyproject.toml (style, line length, import sorting).
• .gitignore updated in website/ for virtualenv/Poetry and local files.

System integration

• Add systemd service templates: etc/systemd/system/misp-modules.service, etc/systemd/system/misp-modules-website.service.
• Run website with Gunicorn using "main:app"; use .env for bind URL/port; stdout/stderr captured to logs.
• Add logrotate configs for service logs.

Removed files

• website/app_creation.py, website/launch.py, website/migrate.py.
• website/conf/config.py, website/conf/config.cfg*.
• website/requirements.txt.

Notes

• Assumes misp-modules is Poetry-managed in the parent directory for --dev.
• Set ADMIN_PASSWORD in .env for production to enable admin features.
• Service and logrotate files are templates; adjust paths/users for deployment.

[DavidCruciani]

I had some troubles to run the app with poetry andthe new main.py so I made changes that I'll push just after merging this PR.
Thanks for your work !