Build Turn Management System

[Junaid-Kureshi]

Complete the turn-based system that alternates between player and dealer.

Requirements:

• Implement switch_turn() function
• Complete is_player_turn() and helper functions
• Emit turn_changed signal when turns switch
• Handle turn validation in game actions

Acceptance Criteria:

• Turns alternate properly between player and dealer
• Turn change signal emits with correct turn value
• Game actions are blocked when it's not the player's turn
• Visual indicator shows whose turn it is

Files to modify:

• scripts/singletons/GameManager.gd

Testing:
Call GameManager.switch_turn() multiple times and verify turn state changes.