fix: integrate final user-provided notification sound and clean up unused assets

- Replaced placeholder audio with the requested high-quality sound file.

- Removed deprecated audio files from the public directory.

debug.txt

@@ -1,12 +1,27 @@
-Look at line 354: `if (req.user.role !== 'super_admin' && rows[0].tenant_id !== req.user.tenant_id) {`
-What if `req.user.tenant_id` is null (which it is for some system admins)?
-But `rows[0].tenant_id` could be something else. That just returns 403.
-What if `rows` is empty?
-Line 353: `if (rows.length === 0) return res.status(404).json({ error: 'Not found' });`
-What if `req.user` is undefined? (Should be caught by middleware).
+Look at `playNotificationSound`:
+```javascript
+  const playNotificationSound = () => {
+    if (currentUser?.sound_enabled !== false && audioRef.current) {
+      // Reset time to 0 to allow rapid replays
+      audioRef.current.currentTime = 0;
+      const playPromise = audioRef.current.play();
+```
+Is `currentUser` loaded when `loadNotifications` fires for the first time after `isInitialLoadRef` is false?
+Yes, `useEffect` calls `fetchCurrentUser()`, which sets `currentUser`.
 
-Wait, the user says the error is:
-`https://fasto.blyzer.com.br/api/users/u_71657ec7`
-And it returns `500`.
+Wait. `setInterval` uses a closure over the state!
+```javascript
+  useEffect(() => {
+    fetchCurrentUser();
+    loadNotifications();
+    const interval = setInterval(loadNotifications, 10000);
+    return () => clearInterval(interval);
+  }, [navigate]);
+```
+Oh my god. The `setInterval` callback `loadNotifications` captures the *initial* state variables, including `currentUser`, which is `null` on the first render!
+If `currentUser` is `null` inside the closure, `currentUser?.sound_enabled !== false` evaluates to `true !== false` which is `true`. So that's not blocking it.
+BUT `audioRef.current` might not have been rendered yet? No, `audioRef` is a ref, so it mutates in place. The closure always sees the latest `audioRef.current`.
 
-Let's log the exact error inside the catch block in the backend.
+So why does it fail or not play? 
+Is the browser policy blocking it silently without logging?
+Let's add a robust, standalone Audio approach that doesn't rely on the DOM tag if it fails, or maybe just force a click handler to "unlock" the audio context.