refactor: migrate ingredient aliases/categories to dedicated tables, drop spoonacular_id

- migration 012: create ingredient_categories + ingredient_category_translations
  tables (7 slugs, Russian names); add ingredient_aliases (ingredient_id, lang,
  alias) with GIN trigram index; migrate aliases JSONB from ingredient_mappings
  and ingredient_translations; drop aliases columns and spoonacular_id; add
  UNIQUE (canonical_name) as conflict key
- ingredient/model: remove SpoonacularID, add CategoryName for localized display
- ingredient/repository: conflict on canonical_name; GetByID/Search join category
  translations and aliases lateral; new UpsertAliases (pgx batch),
  UpsertCategoryTranslation; remove GetBySpoonacularID; split scan helpers into
  scanMappingWrite / scanMappingRead
- gemini/recognition: add IngredientTranslation type; IngredientClassification
  now carries Translations []IngredientTranslation instead of CanonicalNameRu;
  update ClassifyIngredient prompt to English with structured translations array
- recognition/handler: update ingredientRepo interface; saveClassification uses
  UpsertAliases and iterates Translations
- recipe/model: remove SpoonacularID from RecipeIngredient
- integration tests: remove SpoonacularID fixtures, replace GetBySpoonacularID
  tests with GetByID, add UpsertAliases and UpsertCategoryTranslation tests
- Flutter: remove canonicalNameRu from IngredientMapping, add categoryName;
  displayName returns server-resolved canonicalName; regenerate .g.dart

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

backend/migrations/012_refactor_ingredients.sql

@@ -0,0 +1,89 @@
+-- +goose Up
+
+-- 1. ingredient_categories: slug-keyed table (the 7 known slugs)
+CREATE TABLE ingredient_categories (
+    slug       VARCHAR(50) PRIMARY KEY,
+    sort_order SMALLINT    NOT NULL DEFAULT 0
+);
+INSERT INTO ingredient_categories (slug, sort_order) VALUES
+    ('dairy', 1), ('meat', 2), ('produce', 3),
+    ('bakery', 4), ('frozen', 5), ('beverages', 6), ('other', 7);
+
+-- 2. ingredient_category_translations
+CREATE TABLE ingredient_category_translations (
+    category_slug VARCHAR(50) NOT NULL REFERENCES ingredient_categories(slug) ON DELETE CASCADE,
+    lang          VARCHAR(10) NOT NULL,
+    name          TEXT        NOT NULL,
+    PRIMARY KEY (category_slug, lang)
+);
+INSERT INTO ingredient_category_translations (category_slug, lang, name) VALUES
+    ('dairy',     'ru', 'Молочные продукты'),
+    ('meat',      'ru', 'Мясо и птица'),
+    ('produce',   'ru', 'Овощи и фрукты'),
+    ('bakery',    'ru', 'Выпечка и хлеб'),
+    ('frozen',    'ru', 'Замороженные'),
+    ('beverages', 'ru', 'Напитки'),
+    ('other',     'ru', 'Прочее');
+
+-- 3. Nullify any unknown category values before adding FK
+UPDATE ingredient_mappings
+    SET category = NULL
+    WHERE category IS NOT NULL
+      AND category NOT IN (SELECT slug FROM ingredient_categories);
+
+ALTER TABLE ingredient_mappings
+    ADD CONSTRAINT fk_ingredient_category
+    FOREIGN KEY (category) REFERENCES ingredient_categories(slug);
+
+-- 4. ingredient_aliases table
+CREATE TABLE ingredient_aliases (
+    ingredient_id UUID        NOT NULL REFERENCES ingredient_mappings(id) ON DELETE CASCADE,
+    lang          VARCHAR(10) NOT NULL,
+    alias         TEXT        NOT NULL,
+    PRIMARY KEY (ingredient_id, lang, alias)
+);
+CREATE INDEX idx_ingredient_aliases_lookup ON ingredient_aliases (ingredient_id, lang);
+CREATE INDEX idx_ingredient_aliases_trgm   ON ingredient_aliases USING GIN (alias gin_trgm_ops);
+
+-- 5. Migrate English aliases from ingredient_mappings.aliases
+INSERT INTO ingredient_aliases (ingredient_id, lang, alias)
+SELECT im.id, 'en', a.val
+FROM   ingredient_mappings im,
+       jsonb_array_elements_text(im.aliases) a(val)
+ON CONFLICT DO NOTHING;
+
+-- 6. Migrate per-language aliases from ingredient_translations.aliases
+INSERT INTO ingredient_aliases (ingredient_id, lang, alias)
+SELECT it.ingredient_id, it.lang, a.val
+FROM   ingredient_translations it,
+       jsonb_array_elements_text(it.aliases) a(val)
+ON CONFLICT DO NOTHING;
+
+-- 7. Drop aliases JSONB columns
+DROP INDEX IF EXISTS idx_ingredient_mappings_aliases;
+ALTER TABLE ingredient_mappings     DROP COLUMN aliases;
+ALTER TABLE ingredient_translations DROP COLUMN aliases;
+
+-- 8. Drop spoonacular_id
+ALTER TABLE ingredient_mappings DROP COLUMN spoonacular_id;
+
+-- 9. Unique constraint on canonical_name (replaces spoonacular_id as conflict key)
+ALTER TABLE ingredient_mappings
+    ADD CONSTRAINT uq_ingredient_canonical_name UNIQUE (canonical_name);
+
+-- +goose Down
+ALTER TABLE ingredient_mappings DROP CONSTRAINT IF EXISTS uq_ingredient_canonical_name;
+ALTER TABLE ingredient_mappings DROP CONSTRAINT IF EXISTS fk_ingredient_category;
+ALTER TABLE ingredient_mappings ADD COLUMN spoonacular_id INTEGER;
+ALTER TABLE ingredient_translations ADD COLUMN aliases JSONB NOT NULL DEFAULT '[]'::jsonb;
+ALTER TABLE ingredient_mappings     ADD COLUMN aliases JSONB NOT NULL DEFAULT '[]'::jsonb;
+-- Restore aliases JSONB from ingredient_aliases (best-effort)
+UPDATE ingredient_mappings im
+    SET aliases = COALESCE(
+        (SELECT json_agg(ia.alias) FROM ingredient_aliases ia
+         WHERE ia.ingredient_id = im.id AND ia.lang = 'en'),
+        '[]'::json);
+DROP TABLE IF EXISTS ingredient_aliases;
+DROP TABLE IF EXISTS ingredient_category_translations;
+DROP TABLE IF EXISTS ingredient_categories;
+CREATE INDEX idx_ingredient_mappings_aliases ON ingredient_mappings USING GIN (aliases);