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/ingredient/repository.go

@@ -0,0 +1,185 @@
+package ingredient
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// Repository handles persistence for ingredient_mappings.
+type Repository struct {
+	pool *pgxpool.Pool
+}
+
+// NewRepository creates a new Repository.
+func NewRepository(pool *pgxpool.Pool) *Repository {
+	return &Repository{pool: pool}
+}
+
+// Upsert inserts or updates an ingredient mapping.
+// Conflict is resolved on spoonacular_id when set; otherwise a simple insert is done.
+func (r *Repository) Upsert(ctx context.Context, m *IngredientMapping) (*IngredientMapping, error) {
+	query := `
+		INSERT INTO ingredient_mappings (
+			canonical_name, canonical_name_ru, spoonacular_id, aliases,
+			category, default_unit,
+			calories_per_100g, protein_per_100g, fat_per_100g, carbs_per_100g, fiber_per_100g,
+			storage_days
+		) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12)
+		ON CONFLICT (spoonacular_id) DO UPDATE SET
+			canonical_name    = EXCLUDED.canonical_name,
+			aliases           = EXCLUDED.aliases,
+			category          = EXCLUDED.category,
+			default_unit      = EXCLUDED.default_unit,
+			calories_per_100g = EXCLUDED.calories_per_100g,
+			protein_per_100g  = EXCLUDED.protein_per_100g,
+			fat_per_100g      = EXCLUDED.fat_per_100g,
+			carbs_per_100g    = EXCLUDED.carbs_per_100g,
+			fiber_per_100g    = EXCLUDED.fiber_per_100g,
+			storage_days      = EXCLUDED.storage_days,
+			updated_at        = now()
+		RETURNING id, canonical_name, canonical_name_ru, spoonacular_id, aliases,
+			category, default_unit,
+			calories_per_100g, protein_per_100g, fat_per_100g, carbs_per_100g, fiber_per_100g,
+			storage_days, created_at, updated_at`
+
+	row := r.pool.QueryRow(ctx, query,
+		m.CanonicalName, m.CanonicalNameRu, m.SpoonacularID, m.Aliases,
+		m.Category, m.DefaultUnit,
+		m.CaloriesPer100g, m.ProteinPer100g, m.FatPer100g, m.CarbsPer100g, m.FiberPer100g,
+		m.StorageDays,
+	)
+	return scanMapping(row)
+}
+
+// GetBySpoonacularID returns an ingredient mapping by Spoonacular ID.
+// Returns nil, nil if not found.
+func (r *Repository) GetBySpoonacularID(ctx context.Context, id int) (*IngredientMapping, error) {
+	query := `
+		SELECT id, canonical_name, canonical_name_ru, spoonacular_id, aliases,
+			category, default_unit,
+			calories_per_100g, protein_per_100g, fat_per_100g, carbs_per_100g, fiber_per_100g,
+			storage_days, created_at, updated_at
+		FROM ingredient_mappings
+		WHERE spoonacular_id = $1`
+
+	row := r.pool.QueryRow(ctx, query, id)
+	m, err := scanMapping(row)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, nil
+	}
+	return m, err
+}
+
+// GetByID returns an ingredient mapping by UUID.
+// Returns nil, nil if not found.
+func (r *Repository) GetByID(ctx context.Context, id string) (*IngredientMapping, error) {
+	query := `
+		SELECT id, canonical_name, canonical_name_ru, spoonacular_id, aliases,
+			category, default_unit,
+			calories_per_100g, protein_per_100g, fat_per_100g, carbs_per_100g, fiber_per_100g,
+			storage_days, created_at, updated_at
+		FROM ingredient_mappings
+		WHERE id = $1`
+
+	row := r.pool.QueryRow(ctx, query, id)
+	m, err := scanMapping(row)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, nil
+	}
+	return m, err
+}
+
+// Count returns the total number of ingredient mappings.
+func (r *Repository) Count(ctx context.Context) (int, error) {
+	var n int
+	if err := r.pool.QueryRow(ctx, `SELECT count(*) FROM ingredient_mappings`).Scan(&n); err != nil {
+		return 0, fmt.Errorf("count ingredient_mappings: %w", err)
+	}
+	return n, nil
+}
+
+// ListUntranslated returns ingredients without a Russian name, ordered by id.
+func (r *Repository) ListUntranslated(ctx context.Context, limit, offset int) ([]*IngredientMapping, error) {
+	query := `
+		SELECT id, canonical_name, canonical_name_ru, spoonacular_id, aliases,
+			category, default_unit,
+			calories_per_100g, protein_per_100g, fat_per_100g, carbs_per_100g, fiber_per_100g,
+			storage_days, created_at, updated_at
+		FROM ingredient_mappings
+		WHERE canonical_name_ru IS NULL
+		ORDER BY id
+		LIMIT $1 OFFSET $2`
+
+	rows, err := r.pool.Query(ctx, query, limit, offset)
+	if err != nil {
+		return nil, fmt.Errorf("list untranslated: %w", err)
+	}
+	defer rows.Close()
+	return collectMappings(rows)
+}
+
+// UpdateTranslation saves the Russian name and adds Russian aliases.
+func (r *Repository) UpdateTranslation(ctx context.Context, id, canonicalNameRu string, aliasesRu []string) error {
+	// Merge new aliases into existing JSONB array without duplicates
+	query := `
+		UPDATE ingredient_mappings SET
+			canonical_name_ru = $2,
+			aliases = (
+				SELECT jsonb_agg(DISTINCT elem)
+				FROM (
+					SELECT jsonb_array_elements(aliases) AS elem
+					UNION
+					SELECT to_jsonb(unnest) FROM unnest($3::text[]) AS unnest
+				) sub
+			),
+			updated_at = now()
+		WHERE id = $1`
+
+	if _, err := r.pool.Exec(ctx, query, id, canonicalNameRu, aliasesRu); err != nil {
+		return fmt.Errorf("update translation %s: %w", id, err)
+	}
+	return nil
+}
+
+// --- helpers ---
+
+func scanMapping(row pgx.Row) (*IngredientMapping, error) {
+	var m IngredientMapping
+	var aliases []byte
+
+	err := row.Scan(
+		&m.ID, &m.CanonicalName, &m.CanonicalNameRu, &m.SpoonacularID, &aliases,
+		&m.Category, &m.DefaultUnit,
+		&m.CaloriesPer100g, &m.ProteinPer100g, &m.FatPer100g, &m.CarbsPer100g, &m.FiberPer100g,
+		&m.StorageDays, &m.CreatedAt, &m.UpdatedAt,
+	)
+	if err != nil {
+		return nil, err
+	}
+	m.Aliases = json.RawMessage(aliases)
+	return &m, nil
+}
+
+func collectMappings(rows pgx.Rows) ([]*IngredientMapping, error) {
+	var result []*IngredientMapping
+	for rows.Next() {
+		var m IngredientMapping
+		var aliases []byte
+		if err := rows.Scan(
+			&m.ID, &m.CanonicalName, &m.CanonicalNameRu, &m.SpoonacularID, &aliases,
+			&m.Category, &m.DefaultUnit,
+			&m.CaloriesPer100g, &m.ProteinPer100g, &m.FatPer100g, &m.CarbsPer100g, &m.FiberPer100g,
+			&m.StorageDays, &m.CreatedAt, &m.UpdatedAt,
+		); err != nil {
+			return nil, fmt.Errorf("scan mapping: %w", err)
+		}
+		m.Aliases = json.RawMessage(aliases)
+		result = append(result, &m)
+	}
+	return result, rows.Err()
+}