Implement Auth Interceptor

app/src/main/java/core/notevault/sync/ApiClient.java

@@ -1,6 +1,9 @@
 package core.notevault.sync;
 
 import android.content.Context;
+import android.content.SharedPreferences;
+import core.notevault.sync.auth.AuthInterceptor;
+import okhttp3.OkHttpClient;
 import retrofit2.Retrofit;
 import retrofit2.converter.gson.GsonConverterFactory;
 
@@ -9,8 +12,14 @@ public class ApiClient {
 
     public static Retrofit getRetrofitInstance(Context context) {
         if (retrofit == null) {
+            SharedPreferences sharedPreferences = context.getSharedPreferences("app_prefs", Context.MODE_PRIVATE);
+            OkHttpClient client = new OkHttpClient.Builder()
+                    .addInterceptor(new AuthInterceptor(sharedPreferences))
+                    .build();
+
             retrofit = new Retrofit.Builder()
                     .baseUrl("http://192.168.178.30:8080/")
+                    .client(client)
                     .addConverterFactory(GsonConverterFactory.create())
                     .build();
         }

app/src/main/java/core/notevault/sync/auth/AuthInterceptor.java

@@ -0,0 +1,31 @@
+package core.notevault.sync.auth;
+
+import android.content.SharedPreferences;
+import okhttp3.Interceptor;
+import okhttp3.Request;
+import okhttp3.Response;
+
+
+import java.io.IOException;
+
+public class AuthInterceptor implements Interceptor {
+    private SharedPreferences sharedPreferences;
+
+    public AuthInterceptor(SharedPreferences sharedPreferences) {
+        this.sharedPreferences = sharedPreferences;
+    }
+
+    @Override
+    public Response intercept(Chain chain) throws IOException {
+        Request originalRequest = chain.request();
+
+        String token = sharedPreferences.getString("jwt_token", null);
+        if (token == null) {
+            return chain.proceed(originalRequest);
+        }
+
+        Request authenticatedRequest = originalRequest.newBuilder()
+                .header("Authorization", "Bearer " + token).build();
+        return chain.proceed(authenticatedRequest);
+    }
+}