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/002_create_ingredient_mappings.sql

@@ -0,0 +1,36 @@
+-- +goose Up
+CREATE TABLE ingredient_mappings (
+    id                UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+    canonical_name    VARCHAR(255) NOT NULL,
+    canonical_name_ru VARCHAR(255),
+    spoonacular_id    INTEGER UNIQUE,
+
+    aliases           JSONB NOT NULL DEFAULT '[]'::jsonb,
+
+    category          VARCHAR(50),
+    default_unit      VARCHAR(20),
+
+    -- Nutrients per 100g
+    calories_per_100g DECIMAL(8, 2),
+    protein_per_100g  DECIMAL(8, 2),
+    fat_per_100g      DECIMAL(8, 2),
+    carbs_per_100g    DECIMAL(8, 2),
+    fiber_per_100g    DECIMAL(8, 2),
+
+    storage_days      INTEGER,
+
+    created_at        TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at        TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX idx_ingredient_mappings_aliases
+    ON ingredient_mappings USING GIN (aliases);
+
+CREATE INDEX idx_ingredient_mappings_canonical_name
+    ON ingredient_mappings (canonical_name);
+
+CREATE INDEX idx_ingredient_mappings_category
+    ON ingredient_mappings (category);
+
+-- +goose Down
+DROP TABLE IF EXISTS ingredient_mappings;