feat: implement Iteration 1 — AI recipe recommendations

Backend:
- Add Groq LLM client (llama-3.3-70b) for recipe generation with JSON
  retry strategy (retries only on parse errors, not API errors)
- Add Pexels client for parallel photo search per recipe
- Add saved_recipes table (migration 004) with JSONB fields
- Add GET /recommendations endpoint (profile-aware prompt building)
- Add POST/GET/GET{id}/DELETE /saved-recipes CRUD endpoints
- Wire gemini, pexels, recommendation, savedrecipe packages in main.go

Flutter:
- Add Recipe, SavedRecipe models with json_serializable
- Add RecipeService (getRecommendations, getSavedRecipes, save, delete)
- Add RecommendationsNotifier and SavedRecipesNotifier (Riverpod)
- Add RecommendationsScreen with skeleton loading and refresh FAB
- Add RecipeDetailScreen (SliverAppBar, nutrition tooltip, steps with timer)
- Add SavedRecipesScreen with Dismissible swipe-to-delete and empty state
- Update RecipesScreen to TabBar (Recommendations / Saved)
- Add /recipe-detail route outside ShellRoute (no bottom nav)
- Extend ApiClient with getList() and deleteVoid()

Project:
- Add CLAUDE.md with English-only rule for comments and commit messages

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

backend/internal/recipe/model.go

@@ -0,0 +1,62 @@
+package recipe
+
+import (
+	"encoding/json"
+	"time"
+)
+
+// Recipe is a recipe record in the database.
+type Recipe struct {
+	ID            string          `json:"id"`
+	Source        string          `json:"source"` // spoonacular | ai | user
+	SpoonacularID *int            `json:"spoonacular_id"`
+
+	Title         string  `json:"title"`
+	TitleRu       *string `json:"title_ru"`
+	Description   *string `json:"description"`
+	DescriptionRu *string `json:"description_ru"`
+
+	Cuisine      *string `json:"cuisine"`
+	Difficulty   *string `json:"difficulty"` // easy | medium | hard
+	PrepTimeMin  *int    `json:"prep_time_min"`
+	CookTimeMin  *int    `json:"cook_time_min"`
+	Servings     *int    `json:"servings"`
+	ImageURL     *string `json:"image_url"`
+
+	CaloriesPerServing *float64 `json:"calories_per_serving"`
+	ProteinPerServing  *float64 `json:"protein_per_serving"`
+	FatPerServing      *float64 `json:"fat_per_serving"`
+	CarbsPerServing    *float64 `json:"carbs_per_serving"`
+	FiberPerServing    *float64 `json:"fiber_per_serving"`
+
+	Ingredients json.RawMessage `json:"ingredients"` // []RecipeIngredient
+	Steps       json.RawMessage `json:"steps"`       // []RecipeStep
+	Tags        json.RawMessage `json:"tags"`        // []string
+
+	AvgRating   float64   `json:"avg_rating"`
+	ReviewCount int       `json:"review_count"`
+	CreatedBy   *string   `json:"created_by"`
+	CreatedAt   time.Time `json:"created_at"`
+	UpdatedAt   time.Time `json:"updated_at"`
+}
+
+// RecipeIngredient is a single ingredient in a recipe's JSONB array.
+type RecipeIngredient struct {
+	SpoonacularID *int    `json:"spoonacular_id"`
+	MappingID     *string `json:"mapping_id"`
+	Name          string  `json:"name"`
+	NameRu        *string `json:"name_ru"`
+	Amount        float64 `json:"amount"`
+	Unit          string  `json:"unit"`
+	UnitRu        *string `json:"unit_ru"`
+	Optional      bool    `json:"optional"`
+}
+
+// RecipeStep is a single step in a recipe's JSONB array.
+type RecipeStep struct {
+	Number        int     `json:"number"`
+	Description   string  `json:"description"`
+	DescriptionRu *string `json:"description_ru"`
+	TimerSeconds  *int    `json:"timer_seconds"`
+	ImageURL      *string `json:"image_url"`
+}