feat(products): add shopping suggestions feature

- Add POST /api/products/suggest endpoint that analyzes skin condition
  and inventory to suggest product types (e.g., 'Salicylic Acid 2% Masque')
- Add MCP tool get_shopping_suggestions() for MCP clients
- Add 'Suggest' button to Products page in frontend
- Add /products/suggest page with suggestion cards
- Include product type, key ingredients, target concerns, why_needed,
  recommended_time, and frequency in suggestions
- Fix stock logic: sealed products now count as available inventory
- Add legend to clarify ✓ (in stock) vs ✗ (not in stock) markers

frontend/messages/pl.json

@@ -33,6 +33,17 @@
 	"products_title": "Produkty",
 	"products_count": "{count} produktów",
 	"products_addNew": "+ Dodaj produkt",
+	"products_suggest": "Sugeruj",
+	"products_suggestTitle": "Sugestie zakupowe",
+	"products_suggestSubtitle": "Co warto kupić?",
+	"products_suggestDescription": "Na podstawie Twojego stanu skóry i posiadanych produktów zasugeruję typy produktów, które mogłyby uzupełnić Twoją rutynę.",
+	"products_suggestGenerating": "Analizuję...",
+	"products_suggestBtn": "Generuj sugestie",
+	"products_suggestResults": "Propozycje",
+	"products_suggestTime": "Pora",
+	"products_suggestFrequency": "Częstotliwość",
+	"products_suggestRegenerate": "Wygeneruj ponownie",
+	"products_suggestNoResults": "Brak propozycji.",
 	"products_noProducts": "Nie znaleziono produktów.",
 	"products_filterAll": "Wszystkie",
 	"products_filterOwned": "Posiadane",