Add phase 4: AI cleanup and photo/text import via OpenAI

- recipes/ai.py: Chat Completions with strict JSON schema (Structured
  Outputs), Pydantic re-validation, plausibility clamping, prompt treats
  input as data only
- "Mit KI aufbereiten" on create/edit form returns an editable draft
- Import page: photo/screenshot (vision, downscaled JPEG, not stored) and
  pasted text; drafts pre-fill the recipe form with a preview
- Clear UI messages for timeout, rate limit, quota, auth, model and
  connection errors; without OPENAI_API_KEY AI features show a notice
- Optional per-user and global daily AI limits (default unlimited)
- Tests for response parsing, schema strictness, error mapping, views

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

templates/recipes/form.html

@@ -3,17 +3,19 @@
 {% block content %}
 <h1>{% if is_new %}Neues Rezept{% else %}Rezept bearbeiten{% endif %}</h1>
 
-{% block before_form %}{% endblock %}
+{% if draft_notice or ai_draft %}{% include "recipes/_draft_preview.html" %}{% endif %}
 
-<form method="post" enctype="multipart/form-data" class="card recipe-form" novalidate>
+<form method="post"{% if form_action %} action="{{ form_action }}"{% endif %} enctype="multipart/form-data" class="card recipe-form" novalidate>
   {% csrf_token %}
   {% include "form_fields.html" %}
-  {% block form_buttons %}
   <div class="form-buttons">
     <button type="submit" class="button">Speichern</button>
+    {% if ai_enabled %}
+    <button type="submit" name="ai" value="1" class="button secondary" data-busy-text="KI arbeitet …">✨ Mit KI aufbereiten</button>
+    {% endif %}
     <a class="button secondary" href="{% if recipe %}{% url 'recipes:detail' recipe.pk %}{% else %}{% url 'recipes:list' %}{% endif %}">Abbrechen</a>
   </div>
-  {% endblock %}
+  {% if ai_enabled %}<p class="muted small">„Mit KI aufbereiten“ strukturiert deine Eingaben (Zutaten, Schritte, Tags) als Entwurf. Fotos danach auswählen – sie werden dabei nicht übernommen.</p>{% endif %}
 </form>
 
 {% if recipe and images %}