Gate push toggle on backend notification method

Add a GET /api/config endpoint exposing the front-end-facing backend
configuration (currently the notification delivery method, grouped under
a nested "notifications" object so the shape can grow). The settings
screen fetches it on init and only shows the per-device push toggle when
the backend method is "push" (and the platform supports push, which keeps
it off the browser).

Also fold in related push-notifications cleanups: fix the Android app
label ("frontend" -> "OOTT") so the notification permission dialog reads
correctly, remove the completed push_notifications.md plan, and update
TODO.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/model.rs

@@ -1,3 +1,4 @@
+pub mod config;
 pub mod device_events;
 pub mod devices;
 pub mod notifications;

backend/src/model/config.rs

@@ -0,0 +1,17 @@
+use serde::Serialize;
+use utoipa::ToSchema;
+
+// Front-end-facing view of the backend configuration. Only the settings the UI
+// needs to adapt itself are exposed here, grouped by area so the shape can grow
+// without breaking existing fields. Today it carries just the notification
+// method, which gates the per-device push toggle in the settings screen.
+#[derive(Clone, Serialize, ToSchema)]
+pub struct Config {
+    pub notifications: NotificationConfig,
+}
+
+#[derive(Clone, Serialize, ToSchema)]
+pub struct NotificationConfig {
+    // The configured delivery method (e.g. "push", "pushover", "none").
+    pub method: String,
+}

backend/src/web_server.rs

@@ -1,6 +1,7 @@
 use std::error::Error;
 use std::path::{Path, PathBuf};
 
+use crate::model::config::{Config, NotificationConfig};
 use crate::model::device_events::{DeviceEvent, DeviceEventScanner, DeviceEventType};
 use crate::model::devices::{Device, DeviceListResponse, DeviceSummary};
 use crate::model::notifications::{Notification, NotificationListResponse, NotificationType};
@@ -29,6 +30,7 @@ use utoipa::openapi::security::{HttpAuthScheme, HttpBuilder, SecurityScheme};
 use utoipa_swagger_ui::SwaggerUi;
 
 pub mod arp_scanner;
+pub mod config;
 pub mod device_events;
 pub mod devices;
 pub mod dhcp_scanner;
@@ -50,6 +52,7 @@ pub mod utils;
     ),
     paths(
         test_api,
+        config::read,
         devices::list,
         devices::summary,
         devices::read,
@@ -71,6 +74,8 @@ pub mod utils;
         snmp_scanner::status,
     ),
     components(schemas(
+        Config,
+        NotificationConfig,
         Device,
         DeviceListResponse,
         DeviceSummary,
@@ -90,6 +95,7 @@ pub mod utils;
     )),
     modifiers(&SecurityAddon),
     tags(
+        (name = "config", description = "Front-end configuration"),
         (name = "devices", description = "Device management"),
         (name = "notifications", description = "Notification management"),
         (name = "push_tokens", description = "Push notification token registration"),
@@ -163,6 +169,7 @@ pub async fn serve() -> Result<(), Box<dyn Error>> {
 
     let router = Router::new()
         .route("/api/test", get(test_api))
+        .route("/api/config", get(config::read))
         .route("/api/devices", get(devices::list))
         .route("/api/devices", put(devices::register))
         .route("/api/devices/summary", get(devices::summary))

backend/src/web_server/config.rs

@@ -0,0 +1,41 @@
+use axum::Json;
+
+use crate::model::config::{Config, NotificationConfig};
+use crate::settings::get_settings;
+
+#[utoipa::path(
+    get,
+    path = "/api/config",
+    tag = "config",
+    responses(
+        (status = 200, description = "Front-end configuration", body = Config),
+    ),
+    security(("bearer_auth" = []))
+)]
+pub async fn read() -> Json<Config> {
+    let settings = get_settings();
+    Json(Config {
+        notifications: NotificationConfig {
+            method: settings.notifications.method.clone(),
+        },
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::tests_common;
+
+    #[tokio::test]
+    async fn config_reports_the_configured_notification_method() {
+        tests_common::setup().await;
+
+        let Json(config) = read().await;
+
+        assert_eq!(
+            config.notifications.method,
+            get_settings().notifications.method,
+            "The endpoint should echo the backend's configured notification method"
+        );
+    }
+}