feat: product search screen with catalog add and success feedback

- Add product search screen (/products/search) as primary add flow;
  "Add" button on products list opens search, manual entry remains as fallback
- Add to shelf bottom sheet with AnimatedSwitcher success view (green checkmark)
  and SnackBar confirmation on the search screen via onAdded callback
- Manual add (AddProductScreen) shows SnackBar on success before popping back
- Extend AddProductScreen with optional nutrition fields (calories, protein,
  fat, carbs, fiber); auto-fills from catalog selection and auto-expands section
- Auto-upsert catalog product on backend when nutrition data is provided
  without a primary_product_id, linking the user product to the catalog
- Add fiber_per_100g field to CatalogProduct model and CreateRequest
- Add 16 new L10n keys across all 12 locales (addProduct, addManually,
  searchProducts, quantity, storageDays, addToShelf, nutritionOptional,
  calories, protein, fat, carbs, fiber, productAddedToShelf, etc.)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/lib/l10n/app_hi.arb

@@ -172,5 +172,32 @@
   "jobTypeReceipt": "रसीद",
   "jobTypeProducts": "उत्पाद",
   "scanSubmitting": "सबमिट हो रहा है...",
-  "processingProducts": "प्रोसेस हो रहा है..."
+  "processingProducts": "प्रोसेस हो रहा है...",
+  "clearAllProducts": "सब साफ करें",
+  "clearAllConfirmTitle": "सभी उत्पाद साफ करें?",
+  "clearAllConfirmMessage": "सभी उत्पाद स्थायी रूप से हटा दिए जाएंगे।",
+  "addManually": "मैन्युअल",
+  "scan": "स्कैन करें",
+  "addProduct": "जोड़ें",
+  "searchProducts": "उत्पाद खोजें",
+  "searchProductsHint": "उत्पाद का नाम टाइप करें या मैन्युअल रूप से जोड़ें",
+  "noSearchResults": "\"{query}\" के लिए कोई परिणाम नहीं",
+  "@noSearchResults": {
+    "placeholders": {
+      "query": {
+        "type": "String"
+      }
+    }
+  },
+  "quantity": "मात्रा",
+  "storageDays": "भंडारण दिन",
+  "addToShelf": "पेंट्री में जोड़ें",
+  "errorGeneric": "कुछ गलत हो गया",
+  "nutritionOptional": "पोषण मूल्य प्रति 100 ग्राम (वैकल्पिक)",
+  "calories": "कैलोरी",
+  "protein": "प्रोटीन",
+  "fat": "वसा",
+  "carbs": "कार्बोहाइड्रेट",
+  "fiber": "फाइबर",
+  "productAddedToShelf": "पेंट्री में जोड़ा गया"
 }