Enable browser notifications by default and always show them

Default prefs now start enabled with osa-announcements channel on.
Removed visibility check (tab focus) and self-filter so all alerts
trigger a browser notification regardless of who created them.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/hooks/use-browser-notifications.ts

@@ -1,6 +1,5 @@
 import { useCallback, useRef, useSyncExternalStore } from "react";
 import { useMqttRawSubscription } from "@/hooks/use-mqtt";
-import { useAuthContext } from "@/contexts/auth-context";
 
 // ── localStorage sync ────────────────────────────────────────────
 
@@ -12,7 +11,7 @@ interface NotificationPrefs {
   channels: string[];
 }
 
-const DEFAULT_PREFS: NotificationPrefs = { enabled: false, channels: [] };
+const DEFAULT_PREFS: NotificationPrefs = { enabled: true, channels: ["osa-announcements"] };
 
 // Cache the snapshot so useSyncExternalStore gets a stable reference
 let cachedRaw: string | null = null;
@@ -108,7 +107,6 @@ export function useNotificationPreference() {
 
 export function useNotificationTrigger() {
   const { enabled, channels, permissionState } = useNotificationPreference();
-  const { user } = useAuthContext();
 
   const enabledRef = useRef(enabled);
   enabledRef.current = enabled;
@@ -116,16 +114,11 @@ export function useNotificationTrigger() {
   channelsRef.current = channels;
   const permRef = useRef(permissionState);
   permRef.current = permissionState;
-  const userRef = useRef(user);
-  userRef.current = user;
 
   const handleMessage = useCallback(
     (topic: string, payload: Record<string, unknown>) => {
       if (!enabledRef.current || permRef.current !== "granted") return;
 
-      // Don't notify when tab is focused
-      if (document.visibilityState === "visible") return;
-
       // Extract channel from topic: mgmt/notifications/{channel}
       const parts = topic.split("/");
       const channel = parts[parts.length - 1];
@@ -134,16 +127,6 @@ export function useNotificationTrigger() {
       // Check if user is subscribed to this channel
       if (!channelsRef.current.includes(channel)) return;
 
-      // Skip own announcements
-      if (
-        channel === "osa-announcements" &&
-        payload.created_by &&
-        userRef.current &&
-        payload.created_by === (userRef.current as { username?: string }).username
-      ) {
-        return;
-      }
-
       const title = (payload.title as string) || "MGMT Notification";
       const body = (payload.body as string) || "";
       const id = (payload.id as string) || String(Date.now());