K2GO-443 feat(code-addons): add-ons gallery updater on the durable job engine

controller/app/src/main/AndroidManifest.xml

@@ -203,6 +203,15 @@
                 android:value="Downloads the Code on the Go build assets through the co-located server REST engine." />
         </service>
 
+        <service
+            android:name=".addons.presentation.AddonsDownloadService"
+            android:exported="false"
+            android:foregroundServiceType="specialUse">
+            <property
+                android:name="android.app.PROPERTY_SPECIAL_USE_FGS_SUBTYPE"
+                android:value="Downloads the Code on the Go add-ons gallery through the co-located server REST engine." />
+        </service>
+
         <service
             android:name=".redesign.BooksDownloadService"
             android:exported="false"

controller/app/src/main/java/org/appdevforall/k2go/addons/presentation/AddonsDownloadService.java

@@ -0,0 +1,98 @@
+/*
+ * ============================================================================
+ * Name        : AddonsDownloadService.java
+ * Author      : AppDevForAll
+ * Copyright   : Copyright (c) 2026 AppDevForAll
+ * Description : K2GO-443 / K2GO-449. Foreground shell for the Code on the Go add-ons gallery download on
+ *               the durable job engine (a single-item session, type "code-addons"). The generic service
+ *               behavior (onStartCommand dispatch, notification, Host) lives in ContentDownloadServiceBase;
+ *               this subclass only provides the module bits: the session singleton, the action strings,
+ *               the notification text, and the START item (a sentinel, since the box runner reads the
+ *               catalog itself). The heavy work (aria2, resume, verify, swap) runs on the box.
+ * ============================================================================
+ */
+package org.appdevforall.k2go.addons.presentation;
+
+import android.content.Context;
+import android.content.Intent;
+
+import androidx.core.content.ContextCompat;
+
+import org.appdevforall.k2go.R;
+import org.appdevforall.k2go.redesign.ContentDownloadServiceBase;
+import org.appdevforall.k2go.redesign.ContentDownloadSession;
+import org.json.JSONArray;
+import org.json.JSONObject;
+
+public final class AddonsDownloadService extends ContentDownloadServiceBase {
+
+    private static final String CHANNEL_ID = "code_addons_download_channel";
+    private static final int NOTIFICATION_ID = 11;   // distinct: 8 is ForgejoSeedService / CloneShareService (may run concurrently)
+
+    public static final String ACTION_START = "org.appdevforall.k2go.CODE_ADDONS_DOWNLOAD_START";
+    public static final String ACTION_PAUSE = "org.appdevforall.k2go.CODE_ADDONS_DOWNLOAD_PAUSE";
+    public static final String ACTION_RESUME = "org.appdevforall.k2go.CODE_ADDONS_DOWNLOAD_RESUME";
+    public static final String ACTION_CANCEL = "org.appdevforall.k2go.CODE_ADDONS_DOWNLOAD_CANCEL";
+    public static final String ACTION_RETRY = "org.appdevforall.k2go.CODE_ADDONS_DOWNLOAD_RETRY";
+
+    // The box runner reads the catalog itself and ignores the job items, so a single sentinel
+    // satisfies POST /code-addons/download (which requires a non-empty items/ids).
+    private static final String SENTINEL = "add-ons";
+
+    private static final ContentDownloadSession SESSION = new ContentDownloadSession("code-addons");
+
+    /** Adapts to the session listener; the UI passes {@code this::render}. */
+    public interface Listener { void onUpdate(); }
+
+    // ---- static API the UI observes (delegates to the shared session) --------------------------
+    public static boolean isRunning() { return SESSION.isRunning(); }
+    public static boolean isPaused() { return SESSION.isPaused(); }
+    public static boolean hasSession() { return SESSION.hasSession(); }
+    public static boolean isComplete() { return SESSION.isComplete(); }
+    public static boolean hasFailed() { return SESSION.hasFailed(); }
+    public static int percent() { return SESSION.percent(); }
+    public static long speed() { return SESSION.speed(); }
+    public static int reconnectAttempt() { return SESSION.reconnectAttempt(); }
+    public static int reconnectTotal() { return SESSION.reconnectTotal(); }
+    public static void setListener(Listener l) { SESSION.setListener(l == null ? null : l::onUpdate); }
+
+    public static void start(Context ctx) { send(ctx, ACTION_START); }
+    public static void pause(Context ctx) { if (SESSION.isRunning()) send(ctx, ACTION_PAUSE); }
+    public static void resume(Context ctx) { send(ctx, ACTION_RESUME); }
+    public static void cancel(Context ctx) { send(ctx, ACTION_CANCEL); }
+
+    /** Re-queue the failed item and resume (the box resumes the partial via aria2 --continue). */
+    public static void retry(Context ctx) {
+        if (SESSION.requeueFailed() && !SESSION.isRunning()) send(ctx, ACTION_RETRY);
+    }
+
+    public static void finishSession() { SESSION.purge(); }
+
+    private static void send(Context ctx, String action) {
+        ContextCompat.startForegroundService(ctx,
+                new Intent(ctx, AddonsDownloadService.class).setAction(action));
+    }
+
+    // ---- per-module hooks for ContentDownloadServiceBase ---------------------------------------
+    @Override protected ContentDownloadSession session() { return SESSION; }
+    @Override protected int notificationId() { return NOTIFICATION_ID; }
+    @Override protected String channelId() { return CHANNEL_ID; }
+    @Override protected String channelName() { return getString(R.string.k2go_card_code_addons); }
+    @Override protected String notifTitle() { return getString(R.string.k2go_code_addons_updating); }
+    @Override protected String notifText() { return getString(R.string.k2go_card_code_addons); }
+    @Override protected String actionPause() { return ACTION_PAUSE; }
+    @Override protected String actionResume() { return ACTION_RESUME; }
+    @Override protected String actionCancel() { return ACTION_CANCEL; }
+    @Override protected String actionRetry() { return ACTION_RETRY; }
+
+    @Override
+    protected void beginFromIntent(Intent intent) {
+        String[] keys = { "code-addons" };
+        String[] labels = { getString(R.string.k2go_card_code_addons) };
+        long[] sizes = { 0L };   // count-based: the UI shows the item percent directly
+        JSONObject[] bodies = new JSONObject[1];
+        try { bodies[0] = new JSONObject().put("ids", new JSONArray().put(SENTINEL)); }
+        catch (Exception e) { bodies[0] = new JSONObject(); }
+        SESSION.begin(keys, labels, sizes, bodies);
+    }
+}