feat: URL 正規化（#208） (#226)

#208

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #226

backend/db/migrate/20260118144400_add_unique_index_to_url_in_posts.rb

@@ -0,0 +1,6 @@
+class AddUniqueIndexToUrlInPosts < ActiveRecord::Migration[7.1]
+  def change
+    change_column :posts, :url, :string, limit: 768
+    add_index :posts, :url, unique: true, name: 'index_posts_on_url'
+  end
+end

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: 2026_01_12_111800) do
+ActiveRecord::Schema[8.0].define(version: 2026_01_18_144400) 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
@@ -85,7 +85,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_01_12_111800) do
 
   create_table "posts", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "title"
-    t.string "url", limit: 2000, null: false
+    t.string "url", limit: 768, null: false
     t.string "thumbnail_base", limit: 2000
     t.bigint "parent_id"
     t.bigint "uploaded_user_id"
@@ -95,6 +95,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_01_12_111800) do
     t.datetime "updated_at", null: false
     t.index ["parent_id"], name: "index_posts_on_parent_id"
     t.index ["uploaded_user_id"], name: "index_posts_on_uploaded_user_id"
+    t.index ["url"], name: "index_posts_on_url", unique: true
   end
 
   create_table "settings", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|