feat(auth): implement authentication system foundation

Add user authentication infrastructure with login/logout functionality,
session management, and basic user model.

Changes:
- Create users table with email, password_digest, confirmation tokens
- Add Users repository with authentication methods
- Add User entity with authentication helpers
- Implement login form and authentication actions
- Add logout action
- Add BCrypt gem for password hashing
- Update base Action class with authentication helpers
- Add login/logout routes

Next steps: Registration flow, password reset, email confirmation

db/migrate/20240915000008_create_users.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+ROM::SQL.migration do
+  change do
+    create_table :users do
+      primary_key :id
+      foreign_key :player_id, :players, null: false
+      column :email, String, null: false, unique: true
+      column :password_digest, String, null: false
+      column :confirmed, Boolean, default: false
+      column :confirmation_token, String
+      column :confirmation_sent_at, DateTime
+      column :reset_password_token, String
+      column :reset_password_sent_at, DateTime
+      column :failed_login_attempts, Integer, default: 0
+      column :locked_until, DateTime
+      column :last_login_at, DateTime
+      column :last_login_ip, String
+      column :created_at, DateTime, null: false, default: Sequel::CURRENT_TIMESTAMP
+      column :updated_at, DateTime, null: false, default: Sequel::CURRENT_TIMESTAMP
+    end
+
+    add_index :users, :email, unique: true
+    add_index :users, :confirmation_token
+    add_index :users, :reset_password_token
+  end
+end