feat: push selected events to a phone over ntfy

Adds a Notifications tab to Settings so an operator can pick which events
reach their phone, published to a single self-hosted ntfy topic.

The notifier subscribes to the realtime event hub the dashboard already
consumes, so every notifiable event keeps exactly one publisher. Inbound
media had no event, so `media.received` is added and published from the
existing durable `gotImage` gate in the chat service — one notification
per conversation, never repeated when the room re-syncs. It feeds the
in-app notification bell as well.

- Best-effort delivery: a rejecting or unreachable ntfy server is logged
  and never propagated into the path that produced the event.
- Events buffered before the notifier attaches are skipped, so a restart
  cannot replay a backlog to somebody's phone.
- Settings are applied field by field onto the live config object, so a
  save takes effect without a restart.
- The access token is environment-owned (NTFY_AUTH_TOKEN) like the other
  secrets: stripped before the settings record is written, never returned
  by the API, which reports only `hasAuthToken`.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/web/events/event-adapters.ts

@@ -28,6 +28,9 @@ export function createDashboardEventAdapters(hub: DashboardEventPublisher) {
     reply(input: { conversationId: string; id: string; username: string; body?: string }): Published {
       return hub.publish('reply.received', { conversationId: input.conversationId, replyId: input.id, sender: input.username, preview: input.body });
     },
+    mediaReceived(input: { conversationId: string; username: string; count: number }): Published {
+      return hub.publish('media.received', { conversationId: input.conversationId, sender: input.username, count: input.count });
+    },
     sync(input: SyncInput): Published {
       const kind = syncKind(input.kind);
       switch (input.phase) {