feat(ntfy): add admin Notifications settings page with test button

app/controllers/admin/notifications_controller.rb

@@ -0,0 +1,41 @@
+module Admin
+  class NotificationsController < BaseController
+    def show
+      @admin = current_admin
+    end
+
+    def update
+      @admin = current_admin
+      if @admin.update(admin_params)
+        redirect_to admin_notifications_path, notice: "Notification settings saved"
+      else
+        flash.now[:alert] = "Failed to save settings"
+        render :show, status: :unprocessable_entity
+      end
+    end
+
+    def test
+      admin = current_admin
+
+      if admin.ntfy_configured?
+        SendNtfyNotificationJob.perform_now(
+          admin.id,
+          "test_notification",
+          title: "Test notification from MySMSAPio",
+          message: "If you can read this, your ntfy setup is working! Sent at #{Time.current.strftime('%H:%M:%S')}.",
+          priority: 3,
+          tags: [ "tada", "white_check_mark" ]
+        )
+        redirect_to admin_notifications_path, notice: "Test notification sent"
+      else
+        redirect_to admin_notifications_path, alert: "Configure ntfy topic and token first"
+      end
+    end
+
+    private
+
+    def admin_params
+      params.require(:admin_user).permit(:ntfy_enabled, :ntfy_topic, :ntfy_token, :ntfy_server_url)
+    end
+  end
+end