feat(FN-4078): add ntfy access token support to notifications

Adds ntfy access token support to Fusion's notification system, wiring the token through the core settings schema, dashboard UI (SettingsModal), engine notifier, and notification pipeline, with corresponding tests across core, dashboard, and engine packages; also updates settings and storage documen

Fusion-Task-Id: FN-4078

packages/core/src/__tests__/global-settings.test.ts

@@ -169,6 +169,7 @@ describe("GlobalSettingsStore", () => {
       // Defaults are filled in for missing fields
       expect(settings.ntfyEnabled).toBe(false);
       expect(settings.ntfyBaseUrl).toBeUndefined();
+      expect(settings.ntfyAccessToken).toBeUndefined();
       expect(settings.defaultProvider).toBeUndefined();
     });
 
@@ -260,6 +261,23 @@ describe("GlobalSettingsStore", () => {
       expect(settings.ntfyTopic).toBeUndefined();
     });
 
+    it("clearing ntfyAccessToken with null removes it from disk and returns undefined", async () => {
+      await store.init();
+      await store.updateSettings({ ntfyAccessToken: "secret-token" });
+
+      const raw = JSON.parse(await readFile(join(dir, "settings.json"), "utf-8"));
+      expect(raw.ntfyAccessToken).toBe("secret-token");
+
+      // @ts-expect-error - null is intentionally used to clear field (null-as-delete)
+      await store.updateSettings({ ntfyAccessToken: null });
+
+      const rawAfter = JSON.parse(await readFile(join(dir, "settings.json"), "utf-8"));
+      expect(rawAfter.ntfyAccessToken).toBeUndefined();
+
+      const settings = await store.getSettings();
+      expect(settings.ntfyAccessToken).toBeUndefined();
+    });
+
     it("clearing ntfyDashboardHost with null removes it from disk", async () => {
       await store.init();
       await store.updateSettings({ ntfyDashboardHost: "https://dashboard.example.com" });