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/migrations/003_create_recipes.sql

@@ -0,0 +1,58 @@
+-- +goose Up
+CREATE TYPE recipe_source     AS ENUM ('spoonacular', 'ai', 'user');
+CREATE TYPE recipe_difficulty AS ENUM ('easy', 'medium', 'hard');
+
+CREATE TABLE recipes (
+    id             UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+    source         recipe_source NOT NULL DEFAULT 'spoonacular',
+    spoonacular_id INTEGER UNIQUE,
+
+    title          VARCHAR(500) NOT NULL,
+    description    TEXT,
+    title_ru       VARCHAR(500),
+    description_ru TEXT,
+
+    cuisine        VARCHAR(100),
+    difficulty     recipe_difficulty,
+    prep_time_min  INTEGER,
+    cook_time_min  INTEGER,
+    servings       SMALLINT,
+    image_url      TEXT,
+
+    calories_per_serving DECIMAL(8, 2),
+    protein_per_serving  DECIMAL(8, 2),
+    fat_per_serving      DECIMAL(8, 2),
+    carbs_per_serving    DECIMAL(8, 2),
+    fiber_per_serving    DECIMAL(8, 2),
+
+    ingredients JSONB NOT NULL DEFAULT '[]'::jsonb,
+    steps       JSONB NOT NULL DEFAULT '[]'::jsonb,
+    tags        JSONB NOT NULL DEFAULT '[]'::jsonb,
+
+    avg_rating   DECIMAL(3, 2) NOT NULL DEFAULT 0.0,
+    review_count INTEGER NOT NULL DEFAULT 0,
+
+    created_by UUID REFERENCES users (id) ON DELETE SET NULL,
+
+    created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX idx_recipes_title_fts ON recipes
+    USING GIN (to_tsvector('simple',
+        coalesce(title_ru, '') || ' ' || coalesce(title, '')));
+
+CREATE INDEX idx_recipes_ingredients ON recipes USING GIN (ingredients);
+CREATE INDEX idx_recipes_tags        ON recipes USING GIN (tags);
+
+CREATE INDEX idx_recipes_cuisine    ON recipes (cuisine);
+CREATE INDEX idx_recipes_difficulty ON recipes (difficulty);
+CREATE INDEX idx_recipes_prep_time  ON recipes (prep_time_min);
+CREATE INDEX idx_recipes_calories   ON recipes (calories_per_serving);
+CREATE INDEX idx_recipes_source     ON recipes (source);
+CREATE INDEX idx_recipes_rating     ON recipes (avg_rating DESC);
+
+-- +goose Down
+DROP TABLE IF EXISTS recipes;
+DROP TYPE IF EXISTS recipe_difficulty;
+DROP TYPE IF EXISTS recipe_source;