feat: food search sheet with FTS+trgm, dish/recent endpoints, multilingual aliases

Backend:
- GET /dishes/search — hybrid FTS (english + simple) + trgm + ILIKE search
- GET /diary/recent — recently used dishes and products for the current user
- product search upgraded: FTS on canonical_name and product_aliases, ranked by GREATEST(ts_rank, similarity)
- importoff: collect product_name_ru/de/fr/... as product_aliases for multilingual search (e.g. "сникерс" → "Snickers")
- migrations: FTS + trgm indexes merged into 001_initial_schema.sql (002 removed)

Flutter:
- FoodSearchSheet: debounced search field, recently-used section, product/dish results, scan-photo and barcode chips
- DishPortionSheet: quick ½/1/1½/2 buttons + custom input
- + button in meal card now opens FoodSearchSheet instead of going directly to AI scan
- 7 new l10n keys across all 12 languages

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

client/lib/l10n/app_es.arb

@@ -110,5 +110,18 @@
   "portionWeightG": "Peso de la porción (g)",
   "productNotFound": "Producto no encontrado",
   "enterManually": "Ingresar manualmente",
-  "perHundredG": "por 100 g"
+  "perHundredG": "por 100 g",
+  "searchFoodHint": "Buscar productos y platos...",
+  "recentlyUsedLabel": "Usados recientemente",
+  "productsSection": "Productos",
+  "dishesSection": "Platos",
+  "noResultsForQuery": "Nada encontrado para \"{query}\"",
+  "@noResultsForQuery": {
+    "placeholders": {
+      "query": { "type": "String" }
+    }
+  },
+  "servingsLabel": "Porciones",
+  "addToDiary": "Añadir al diario",
+  "scanDishPhoto": "Escanear foto"
 }