Update django-migrations to Django 6.1

[realpython-bot]

Brings django-migrations/ in line with the maintenance update of Django Migrations: A Primer, which moves the tutorial from Django 2.1 to Django 6.1.

Changes

• Regenerated the bitcoin_tracker project scaffold with django-admin startproject on Django 6.1.2 — adds asgi.py, and updates settings.py, urls.py, wsgi.py, and manage.py to the current templates.
• Regenerated both migrations by following the tutorial's steps on Django 6.1.2: 0001_initial (model with PositiveIntegerField), then 0002_switch_to_decimals via makemigrations --name switch_to_decimals.
• Added a pinned requirements.txt (Django==6.1.2, asgiref==3.12.1, sqlparse==0.6.0).
• Rewrote the README's install section into ## Setup / ## Usage with the new versions.
• db.sqlite3 is left untouched — verified that it migrates cleanly under the new code (applies auth.0010–0012).

The follow-up Digging Deeper Into Django Migrations also uses this folder; its pending update targets Django 6.1 as well.

Verification

Fresh Python 3.14 venv, pip install -r requirements.txt, then on a fresh database:

• python manage.py check → no issues
• python manage.py migrate → all migrations apply, including historical_data.0002_switch_to_decimals
• python manage.py makemigrations --check --dry-run → no changes detected
• ruff@0.14.1 format --check and ruff check pass

Console output while walking through the tutorial (makemigrations +/~ markers, migration names, sqlmigrate) matches the updated article.

Reviewed by Martin Breuss.

🤖 Generated with Claude Code

[realpython-bot]

Closing as a duplicate of #836, which already syncs django-migrations/ to Django 6.1 for both Django Migrations: A Primer and Digging Deeper Into Django Migrations (and has the migration files formatted to house style). The one thing this PR added — pinning Django==6.1.2 — is now pushed to #836 as e617709.