Fix transaction to wrap Migration.new

Move the transaction from the instance `run` method to `self.run` so
it wraps both initialization and execution. This ensures database
operations in `initialize` are rolled back on failure.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: MatheusRich

lib/data_customs/migration.rb

@@ -5,20 +5,22 @@ class Migration
     DEFAULT_BATCH_SIZE = 1000
     DEFAULT_THROTTLE = 0.01
 
-    def self.run(...) = new(...).run
+    def self.run(...)
+      ActiveRecord::Base.transaction do
+        new(...).run
+      end
+    rescue => e
+      warn "🛃 Data migration failed"
+      raise e
+    end
 
     def up = raise NotImplementedError
     def verify! = raise NotImplementedError
 
     def run
-      ActiveRecord::Base.transaction do
-        up
-        verify!
-        puts "🛃 Data migration ran successfully!"
-      rescue => e
-        warn "🛃 Data migration failed"
-        raise e
-      end
+      up
+      verify!
+      puts "🛃 Data migration ran successfully!"
     end
 
     private

spec/data_customs/migration_spec.rb

@@ -52,6 +52,21 @@ def verify! = raise "Should not reach this"
       .and raise_error("Kaboom")
   end
 
+  it "rolls back db operations in initialize if up fails" do
+    migration = Class.new(DataCustoms::Migration) do
+      def initialize
+        TestUser.create!(name: "Created in initialize")
+      end
+
+      def up = raise "Kaboom"
+      def verify! = nil
+    end
+
+    expect { migration.run }
+      .to raise_error("Kaboom")
+      .and change { TestUser.count }.by(0)
+  end
+
   describe "helpers" do
     it "batches records" do
       3.times { |i| TestUser.create!(name: "User #{i}") }