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>

config.yaml

@@ -59,6 +59,22 @@ conversations:
     killConfidence: 0.8
     flagConfidence: 0.6
 
+pushNotifications:
+  # Phone push via ntfy. The topic is world-readable to anyone who guesses it,
+  # so use an unguessable name. Set NTFY_AUTH_TOKEN for a protected topic.
+  enabled: false
+  serverUrl: "https://ntfy.sh"   # Point at your self-hosted instance
+  topic: ""                      # e.g. redditbot-7f3a9c21
+  priority: default              # min | low | default | high | max
+  events:
+    imageReceived: true
+    replyReceived: false
+    messageFailed: false
+    botStopped: false
+    rateLimited: false
+    sessionExpired: true
+    syncFailed: false
+
 openrouter:
   imageAnalysisModel: "google/gemini-2.5-flash-lite"
   imageAnalysisFallbackModels: