fix(android): unify notification channel ID across components

- Change ChannelManager DEFAULT_CHANNEL_ID from 'daily_default' to 'timesafari.daily'
- Ensures consistent channel ID usage across Plugin, ChannelManager, and Receivers
- Removes duplicate channel creation - ChannelManager is now single source of truth

android/plugin/src/main/java/com/timesafari/dailynotification/ChannelManager.java

@@ -21,7 +21,7 @@ import android.util.Log;
  */
 public class ChannelManager {
     private static final String TAG = "ChannelManager";
-    private static final String DEFAULT_CHANNEL_ID = "daily_default";
+    private static final String DEFAULT_CHANNEL_ID = "timesafari.daily";
     private static final String DEFAULT_CHANNEL_NAME = "Daily Notifications";
     private static final String DEFAULT_CHANNEL_DESCRIPTION = "Daily notifications from TimeSafari";