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

app/action.rb

@@ -5,5 +5,43 @@ require "hanami/action"
 
 module EuchreCamp
   class Action < Hanami::Action
+    include Deps[users_repo: 'repositories.users', players_repo: 'repositories.players']
+
+    protected
+
+    # Get current user from session
+    def current_user(request)
+      user_id = request.session[:user_id]
+      return nil unless user_id
+
+      users_repo.by_id(user_id)
+    end
+
+    # Get current player from session
+    def current_player(request)
+      player_id = request.session[:player_id]
+      return nil unless player_id
+
+      players_repo.by_id(player_id)
+    end
+
+    # Check if user is logged in
+    def logged_in?(request)
+      !request.session[:user_id].nil?
+    end
+
+    # Require authentication - redirect to login if not logged in
+    def require_authentication(request, response)
+      unless logged_in?(request)
+        response.flash[:error] = 'Please login to continue'
+        response.redirect_to '/login'
+      end
+    end
+
+    # Helper to pass current_player to view
+    def render_with_player(request, response, **options)
+      player = current_player(request)
+      response.render(view, current_player: player, **options)
+    end
   end
 end