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/base.html

@@ -11,12 +11,12 @@
 </head>
 <body>
   <header class="topbar">
-    <a class="brand" href="{% url 'core:home' %}">Kochbuch</a>
+    <a class="brand" href="{% url 'recipes:list' %}">Kochbuch</a>
     {% if user.is_authenticated %}
     <details class="menu">
       <summary aria-label="Menü">☰</summary>
       <nav>
-        <a href="{% url 'core:home' %}">Rezepte</a>
+        <a href="{% url 'recipes:list' %}">Rezepte</a>
         <a href="{% url 'accounts:profile' %}">Mein Konto</a>
         {% if user.is_admin %}
         <a href="{% url 'accounts:admin_users' %}">Nutzer verwalten</a>