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/en.json

@@ -33,6 +33,17 @@
 	"products_title": "Products",
 	"products_count": "{count} products",
 	"products_addNew": "+ Add product",
+	"products_suggest": "Suggest",
+	"products_suggestTitle": "Shopping suggestions",
+	"products_suggestSubtitle": "What to buy?",
+	"products_suggestDescription": "Based on your skin condition and products you own, I'll suggest product types that could complement your routine.",
+	"products_suggestGenerating": "Analyzing...",
+	"products_suggestBtn": "Generate suggestions",
+	"products_suggestResults": "Suggestions",
+	"products_suggestTime": "Time",
+	"products_suggestFrequency": "Frequency",
+	"products_suggestRegenerate": "Regenerate",
+	"products_suggestNoResults": "No suggestions.",
 	"products_noProducts": "No products found.",
 	"products_filterAll": "All",
 	"products_filterOwned": "Owned",