Add phase 2: recipes with visibility, photos, search and favourites

- Recipe model with ingredients (amount/range, unit, group, note), steps,
  lowercase tags, author notes, source URL and private/public visibility
- Central RecipeQuerySet.visible_to() used by every read path; edit only
  by owner, delete by owner or admin (visible recipes only)
- Text-based editing: ingredient/step parser with roundtrip and scaling
- Photo upload (JPEG/PNG/WebP/HEIC), re-encoded to WebP without EXIF,
  thumbnails, cover image, served only through permission-checked view
- Search across title, description, ingredients, tags; ingredient and tag
  filters; "mine" and favourites views
- Admin can delete all recipes of a deactivated user
- Acceptance tests: private recipes unreachable for others and admins
  in list, search, tags, favourites, detail, edit, delete and image URLs

Co-Authored-By: Claude Opus 5.5 <[email protected]>

templates/errors/403.html

@@ -3,5 +3,5 @@
 {% block content %}
 <h1>Kein Zugriff</h1>
 <p>Dafür fehlen dir die Berechtigungen.</p>
-<p><a href="{% url 'core:home' %}">Zur Startseite</a></p>
+<p><a href="{% url 'recipes:list' %}">Zur Startseite</a></p>
 {% endblock %}

templates/errors/404.html

@@ -3,5 +3,5 @@
 {% block content %}
 <h1>Nicht gefunden</h1>
 <p>Diese Seite gibt es nicht oder du hast keinen Zugriff darauf.</p>
-<p><a href="{% url 'core:home' %}">Zur Startseite</a></p>
+<p><a href="{% url 'recipes:list' %}">Zur Startseite</a></p>
 {% endblock %}