add MCP support

db/migrate/20260224120000_add_pkce_to_doorkeeper_access_grants.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class AddPkceToDoorkeeperAccessGrants < ActiveRecord::Migration[7.1]
+  def change
+    add_column :oauth_access_grants, :code_challenge, :string, null: true
+    add_column :oauth_access_grants, :code_challenge_method, :string, null: true
+  end
+end

db/migrate/20260226193537_create_mcp_tokens.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class CreateMcpTokens < ActiveRecord::Migration[8.1]
+  def change
+    create_table :mcp_tokens do |t|
+      t.references :user, null: false, foreign_key: true, index: true
+      t.string :name, null: false
+      t.string :sha256, null: false, index: { unique: true }
+      t.string :token_prefix, null: false
+      t.datetime :archived_at
+
+      t.timestamps
+    end
+  end
+end