Handle SMSG_ACHIEVEMENT_EARNED with toast banner and chat notification

- Parse SMSG_ACHIEVEMENT_EARNED (guid + achievementId + PackedTime date)
  and fire AchievementEarnedCallback for self, chat notify for others
- Add renderAchievementToast() to GameScreen: slides in from right,
  gold-bordered panel with "Achievement Earned!" title + ID, 5s duration
  with 0.4s slide-in/out animation and fade at end
- Add triggerAchievementToast(uint32_t) public method on GameScreen
- Wire AchievementEarnedCallback in application.cpp
- Add playAchievementAlert() to UiSoundManager, loads
  Sound\Interface\AchievementSound.wav with level-up fallback
- SMSG_ALL_ACHIEVEMENT_DATA silently consumed (no tracker UI yet)

include/audio/ui_sound_manager.hpp

@@ -67,6 +67,9 @@ public:
     // Level up
     void playLevelUp();
 
+    // Achievement
+    void playAchievementAlert();
+
     // Error/feedback
     void playError();
     void playTargetSelect();
@@ -114,6 +117,7 @@ private:
     std::vector<UISample> drinkingSounds_;
 
     std::vector<UISample> levelUpSounds_;
+    std::vector<UISample> achievementSounds_;
 
     std::vector<UISample> errorSounds_;
     std::vector<UISample> selectTargetSounds_;