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]>

recipes/forms.py

@@ -81,9 +81,10 @@ class RecipeForm(forms.ModelForm):
         self.fields["servings"].min_value = 1
         recipe = self.instance
         if recipe.pk and not self.is_bound:
-            self.initial["ingredients_text"] = parsing.ingredients_to_text(recipe.ingredients.all())
-            self.initial["steps_text"] = parsing.steps_to_text([s.text for s in recipe.steps.all()])
-            self.initial["tags_text"] = ", ".join(t.name for t in recipe.tags.all())
+            # setdefault: an AI draft passed as initial wins over the stored values
+            self.initial.setdefault("ingredients_text", parsing.ingredients_to_text(recipe.ingredients.all()))
+            self.initial.setdefault("steps_text", parsing.steps_to_text([s.text for s in recipe.steps.all()]))
+            self.initial.setdefault("tags_text", ", ".join(t.name for t in recipe.tags.all()))
         if recipe.pk:
             remaining = settings.IMAGE_MAX_PER_RECIPE - recipe.images.count()
             self.fields["photos"].label = "Weitere Fotos"