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/savedrecipe/repository.go

@@ -0,0 +1,173 @@
+package savedrecipe
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// ErrNotFound is returned when a saved recipe does not exist for the given user.
+var ErrNotFound = errors.New("saved recipe not found")
+
+// Repository handles persistence for saved recipes.
+type Repository struct {
+	pool *pgxpool.Pool
+}
+
+// NewRepository creates a new Repository.
+func NewRepository(pool *pgxpool.Pool) *Repository {
+	return &Repository{pool: pool}
+}
+
+// Save persists a recipe for userID and returns the stored record.
+func (r *Repository) Save(ctx context.Context, userID string, req SaveRequest) (*SavedRecipe, error) {
+	const query = `
+		INSERT INTO saved_recipes (
+			user_id, title, description, cuisine, difficulty,
+			prep_time_min, cook_time_min, servings, image_url,
+			ingredients, steps, tags, nutrition, source
+		) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14)
+		RETURNING id, user_id, title, description, cuisine, difficulty,
+			prep_time_min, cook_time_min, servings, image_url,
+			ingredients, steps, tags, nutrition, source, saved_at`
+
+	description := nullableStr(req.Description)
+	cuisine := nullableStr(req.Cuisine)
+	difficulty := nullableStr(req.Difficulty)
+	imageURL := nullableStr(req.ImageURL)
+	prepTime := nullableInt(req.PrepTimeMin)
+	cookTime := nullableInt(req.CookTimeMin)
+	servings := nullableInt(req.Servings)
+
+	source := req.Source
+	if source == "" {
+		source = "ai"
+	}
+
+	ingredients := defaultJSONArray(req.Ingredients)
+	steps := defaultJSONArray(req.Steps)
+	tags := defaultJSONArray(req.Tags)
+
+	row := r.pool.QueryRow(ctx, query,
+		userID, req.Title, description, cuisine, difficulty,
+		prepTime, cookTime, servings, imageURL,
+		ingredients, steps, tags, req.Nutrition, source,
+	)
+	return scanRow(row)
+}
+
+// List returns all saved recipes for userID ordered by saved_at DESC.
+func (r *Repository) List(ctx context.Context, userID string) ([]*SavedRecipe, error) {
+	const query = `
+		SELECT id, user_id, title, description, cuisine, difficulty,
+			prep_time_min, cook_time_min, servings, image_url,
+			ingredients, steps, tags, nutrition, source, saved_at
+		FROM saved_recipes
+		WHERE user_id = $1
+		ORDER BY saved_at DESC`
+
+	rows, err := r.pool.Query(ctx, query, userID)
+	if err != nil {
+		return nil, fmt.Errorf("list saved recipes: %w", err)
+	}
+	defer rows.Close()
+
+	var result []*SavedRecipe
+	for rows.Next() {
+		rec, err := scanRows(rows)
+		if err != nil {
+			return nil, fmt.Errorf("scan saved recipe: %w", err)
+		}
+		result = append(result, rec)
+	}
+	return result, rows.Err()
+}
+
+// GetByID returns the saved recipe with id for userID, or nil if not found.
+func (r *Repository) GetByID(ctx context.Context, userID, id string) (*SavedRecipe, error) {
+	const query = `
+		SELECT id, user_id, title, description, cuisine, difficulty,
+			prep_time_min, cook_time_min, servings, image_url,
+			ingredients, steps, tags, nutrition, source, saved_at
+		FROM saved_recipes
+		WHERE id = $1 AND user_id = $2`
+
+	rec, err := scanRow(r.pool.QueryRow(ctx, query, id, userID))
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, nil
+	}
+	return rec, err
+}
+
+// Delete removes the saved recipe with id for userID.
+// Returns ErrNotFound if the record does not exist.
+func (r *Repository) Delete(ctx context.Context, userID, id string) error {
+	tag, err := r.pool.Exec(ctx,
+		`DELETE FROM saved_recipes WHERE id = $1 AND user_id = $2`,
+		id, userID,
+	)
+	if err != nil {
+		return fmt.Errorf("delete saved recipe: %w", err)
+	}
+	if tag.RowsAffected() == 0 {
+		return ErrNotFound
+	}
+	return nil
+}
+
+// --- helpers ---
+
+type scannable interface {
+	Scan(dest ...any) error
+}
+
+func scanRow(s scannable) (*SavedRecipe, error) {
+	var rec SavedRecipe
+	var ingredients, steps, tags, nutrition []byte
+	err := s.Scan(
+		&rec.ID, &rec.UserID, &rec.Title, &rec.Description, &rec.Cuisine, &rec.Difficulty,
+		&rec.PrepTimeMin, &rec.CookTimeMin, &rec.Servings, &rec.ImageURL,
+		&ingredients, &steps, &tags, &nutrition,
+		&rec.Source, &rec.SavedAt,
+	)
+	if err != nil {
+		return nil, err
+	}
+	rec.Ingredients = json.RawMessage(ingredients)
+	rec.Steps = json.RawMessage(steps)
+	rec.Tags = json.RawMessage(tags)
+	if len(nutrition) > 0 {
+		rec.Nutrition = json.RawMessage(nutrition)
+	}
+	return &rec, nil
+}
+
+// scanRows wraps pgx.Rows to satisfy the scannable interface.
+func scanRows(rows pgx.Rows) (*SavedRecipe, error) {
+	return scanRow(rows)
+}
+
+func nullableStr(s string) *string {
+	if s == "" {
+		return nil
+	}
+	return &s
+}
+
+func nullableInt(n int) *int {
+	if n <= 0 {
+		return nil
+	}
+	return &n
+}
+
+func defaultJSONArray(raw json.RawMessage) json.RawMessage {
+	if len(raw) == 0 {
+		return json.RawMessage(`[]`)
+	}
+	return raw
+}