feat: 上位タグのバグ修正（#174） (#175)

#174 エラー回避と誤記修正

#174 完了

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #175

backend/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2025_10_09_222200) do
+ActiveRecord::Schema[8.0].define(version: 2025_12_10_123200) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -120,6 +120,7 @@ ActiveRecord::Schema[8.0].define(version: 2025_10_09_222200) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.index ["parent_tag_id"], name: "index_tag_implications_on_parent_tag_id"
+    t.index ["tag_id", "parent_tag_id"], name: "index_tag_implications_on_tag_id_and_parent_tag_id", unique: true
     t.index ["tag_id"], name: "index_tag_implications_on_tag_id"
   end