feat(fetcher): add configureNativeFetcher cross-platform API

Add configureNativeFetcher() plugin method to enable TypeScript configuration
of native fetchers with API credentials. This provides a cross-platform
mechanism for passing configuration from JavaScript to native code without
relying on platform-specific storage.

- Add configure() method to NativeNotificationContentFetcher interface
  (optional, defaults to no-op for fetchers that don't need config)
- Add configureNativeFetcher plugin method in DailyNotificationPlugin
- Add TypeScript definitions and comprehensive JSDoc
- Create NATIVE_FETCHER_CONFIGURATION.md documentation
- Update TestNativeFetcher to use real API endpoint (10.0.2.2:3000)
- Update DemoNativeFetcher Javadoc explaining configure() is optional
- Add configureNativeFetcher() call to demo app's configurePlugin()

Enables host apps to configure native fetchers from TypeScript, keeping
the interface consistent across Android, iOS, and web platforms.

android/app/src/main/java/com/timesafari/dailynotification/DemoNativeFetcher.java

@@ -25,11 +25,23 @@ import java.util.concurrent.CompletableFuture;
  * 
  * Returns mock notification content for demonstration. In production host apps,
  * this would fetch from TimeSafari API or other data sources.
+ * 
+ * <p><b>Configuration:</b></p>
+ * <p>This fetcher does NOT override {@code configure()} because it uses hardcoded
+ * mock data and doesn't need API credentials. The default no-op implementation
+ * from the interface is sufficient.</p>
+ * 
+ * <p>For an example that accepts configuration from TypeScript, see
+ * {@code TestNativeFetcher} in the test app.</p>
  */
 public class DemoNativeFetcher implements NativeNotificationContentFetcher {
     
     private static final String TAG = "DemoNativeFetcher";
     
+    // Note: We intentionally do NOT override configure() because this fetcher
+    // uses hardcoded mock data. The default no-op implementation from the
+    // interface is sufficient. This demonstrates that configure() is optional.
+    
     @Override
     @NonNull
     public CompletableFuture<List<NotificationContent>> fetchContent(