feat(candy-survival): toggle-and-walk knock mode, unified animations, score rewards, RPC fix

- Changed knock from instant-ambush to toggle-and-walk: press Q to toggle Knock Mode ON, walk into target to execute, consumed on use
- Unified knock animation with other game modes (attack_mode SFX, bump, 3-tile knockback, stagger)
- Added +100 score rewards for completing goals, KNOCK, and GHOST
- Fixed RPC unknown peer ID crash for AI bots in ghost/candy stack sync
- Bots auto-toggle is_charged_strike when they have knock charges
- Fixed profile panel username update on connected peers
- Added SafeNakamaMultiplayerBridge for match state crash prevention

scripts/managers/user_profile_manager.gd

@@ -216,10 +216,9 @@ func update_display_name(new_name: String) -> bool:
 		emit_signal("profile_updated")
 		return true
 	
-	var formatted_username = new_name.replace(" ", "_").to_lower()
 	var result: NakamaAsyncResult = await NakamaManager.client.update_account_async(
 		NakamaManager.session,
-		formatted_username, # username (sync to display name)
+		null, # username (keep existing unique username unchanged)
 		new_name # display_name
 	)
 	
@@ -228,6 +227,7 @@ func update_display_name(new_name: String) -> bool:
 		return false
 	
 	profile["display_name"] = new_name
+	await _save_profile_data()
 	emit_signal("profile_updated")
 	return true