feat: core schema redesign — dishes, structured recipes, cuisines, tags (iteration 7)

Replaces the flat JSONB-based recipe schema with a normalized relational model:

Schema (migrations consolidated to 001_initial_schema + 002_seed_data):
- New: dishes, dish_translations, dish_tags — canonical dish catalog
- New: cuisines, tags, dish_categories with _translations tables + full seed data
- New: recipe_ingredients, recipe_steps with _translations (replaces JSONB blobs)
- New: user_saved_recipes thin bookmark (drops saved_recipes + saved_recipe_translations)
- New: product_ingredients M2M table
- recipes: now a cooking variant of a dish (dish_id FK, no title/JSONB columns)
- recipe_translations: repurposed to per-language notes only
- products: mapping_id → primary_ingredient_id
- menu_items: recipe_id FK → recipes; adds dish_id
- meal_diary: adds dish_id, recipe_id → recipes, portion_g

Backend (Go):
- New packages: internal/cuisine, internal/tag, internal/dish (registry + handler + repo)
- New GET /cuisines, GET /tags (public), GET /dishes, GET /dishes/{id}, GET /recipes/{id}
- recipe, savedrecipe, menu, diary, product, ingredient packages updated for new schema

Flutter:
- New models: Cuisine, Tag; new providers: cuisineNamesProvider, tagNamesProvider
- recipe.dart: RecipeIngredient gains unit_code + effectiveUnit getter
- saved_recipe.dart: thin model, manual fromJson, computed nutrition getter
- diary_entry.dart: adds dishId, recipeId, portionG
- recipe_detail_screen.dart: localized cuisine/tag names via providers

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

backend/internal/server/server.go

@@ -5,12 +5,16 @@ import (
 	"net/http"
 
 	"github.com/food-ai/backend/internal/auth"
+	"github.com/food-ai/backend/internal/cuisine"
 	"github.com/food-ai/backend/internal/diary"
+	"github.com/food-ai/backend/internal/dish"
 	"github.com/food-ai/backend/internal/home"
 	"github.com/food-ai/backend/internal/ingredient"
 	"github.com/food-ai/backend/internal/language"
 	"github.com/food-ai/backend/internal/menu"
 	"github.com/food-ai/backend/internal/middleware"
+	"github.com/food-ai/backend/internal/recipe"
+	"github.com/food-ai/backend/internal/tag"
 	"github.com/food-ai/backend/internal/units"
 	"github.com/food-ai/backend/internal/product"
 	"github.com/food-ai/backend/internal/recognition"
@@ -33,6 +37,8 @@ func NewRouter(
 	menuHandler *menu.Handler,
 	diaryHandler *diary.Handler,
 	homeHandler *home.Handler,
+	dishHandler *dish.Handler,
+	recipeHandler *recipe.Handler,
 	authMiddleware func(http.Handler) http.Handler,
 	allowedOrigins []string,
 ) *chi.Mux {
@@ -49,6 +55,8 @@ func NewRouter(
 	r.Get("/health", healthCheck(pool))
 	r.Get("/languages", language.List)
 	r.Get("/units", units.List)
+	r.Get("/cuisines", cuisine.List)
+	r.Get("/tags", tag.List)
 	r.Route("/auth", func(r chi.Router) {
 		r.Post("/login", authHandler.Login)
 		r.Post("/refresh", authHandler.Refresh)
@@ -81,6 +89,13 @@ func NewRouter(
 			r.Delete("/{id}", productHandler.Delete)
 		})
 
+		r.Route("/dishes", func(r chi.Router) {
+			r.Get("/", dishHandler.List)
+			r.Get("/{id}", dishHandler.GetByID)
+		})
+
+		r.Get("/recipes/{id}", recipeHandler.GetByID)
+
 		r.Route("/menu", func(r chi.Router) {
 			r.Get("/", menuHandler.GetMenu)
 			r.Put("/items/{id}", menuHandler.UpdateMenuItem)