feat: zero-waste tips during cooking mode (#76)

api/index.php

@@ -4458,13 +4458,14 @@ REGOLE:
 6. Includi nella lista ingredienti TUTTI quelli citati nei passi (tranne acqua/sale/pepe/olio).
 7. Language rule: {$recipeLangName} only for all textual fields (`title`, `tags`, `expiry_note`, `ingredients.qty`, `steps`, `nutrition_note`, `tools_needed`). Keep `meal` unchanged.
 8. `tools_needed`: array of kitchen tools/appliances actually required by this recipe (e.g. ["Forno","Frullatore"]). Use the same language as all other text fields. Empty array [] if only stovetop/knife/pan needed.
+9. `zero_waste_tips`: array of zero-waste tips for steps that generate reusable scraps (peels, leftover cooking water, egg whites, cheese rinds, bread crusts, vegetable tops, etc.). Each entry: {"step": 0-based_step_index, "scrap": "scrap name", "tip": "short practical reuse tip (max 20 words)"}. Use the same language as other text fields. Empty array [] if no reusable scraps are generated.
 
 DISPENSA:
 $ingredientsText
 
 Rispondi SOLO JSON valido (no markdown):
 {$promptLanguageRule}
-{"title":"…","meal":"$mealType","persons":$persons,"prep_time":"…","cook_time":"…","tags":["…"],"expiry_note":"…","tools_needed":["…"],"ingredients":[{"name":"…","qty":"200 g","qty_number":200,"from_pantry":true}],"steps":["{$promptStepExample}"],"nutrition_note":"…"}
+{"title":"…","meal":"$mealType","persons":$persons,"prep_time":"…","cook_time":"…","tags":["…"],"expiry_note":"…","tools_needed":["…"],"ingredients":[{"name":"…","qty":"200 g","qty_number":200,"from_pantry":true}],"steps":["{$promptStepExample}"],"nutrition_note":"…","zero_waste_tips":[{"step":0,"scrap":"…","tip":"…"}]}
 PROMPT;
 
     $genConfig = [