Fix: notification sound preview - base-path prefix + longer default beep

The sound picker's preview always played the default beep, even for the other choices, on a subpath deployment.

playFile() used a raw '/notification/x.mp3' path, which 404s under a deployment base path (e.g. /webmail); audio.play() then rejected and fell back to the beep for every non-default choice. Prefix the file with withBasePath().

The default beep was a 150 ms tone with no envelope - easy to miss on Bluetooth outputs, whose audio path can take 100-200 ms to wake up and route. Lengthen it to ~0.45 s with a fade in/out (also removes click artifacts).

lib/notification-sound.ts

@@ -1,4 +1,5 @@
 import { debug } from '@/lib/debug';
+import { withBasePath } from '@/lib/browser-navigation';
 
 export type NotificationSoundChoice = 'default' | 'cheerful' | 'involved' | 'swift' | 'relax';
 
@@ -20,15 +21,29 @@ function playBeep() {
 
   oscillator.frequency.value = 800;
   oscillator.type = 'sine';
-  gainNode.gain.value = 0.1;
 
-  oscillator.start();
+  // Longer, enveloped tone. A 150 ms blip was easy to miss on Bluetooth
-  oscillator.stop(audioContext.currentTime + 0.15);
+  // outputs, whose audio path can take 100-200 ms to wake up and route - by
+  // the time sound reached the headphones the blip was already over. The
+  // fade in/out also avoids click artifacts.
+  const now = audioContext.currentTime;
+  const duration = 0.45;
+  const peak = 0.12;
+  gainNode.gain.setValueAtTime(0.0001, now);
+  gainNode.gain.exponentialRampToValueAtTime(peak, now + 0.04);
+  gainNode.gain.setValueAtTime(peak, now + duration - 0.08);
+  gainNode.gain.exponentialRampToValueAtTime(0.0001, now + duration);
+
+  oscillator.start(now);
+  oscillator.stop(now + duration + 0.02);
   oscillator.onended = () => audioContext.close();
 }
 
 function playFile(file: string) {
-  const audio = new Audio(file);
+  // Prefix with the deployment base path (e.g. /webmail); a raw "/notification/
+  // x.mp3" 404s under a subpath, which made playFile fall back to the beep for
+  // every choice.
+  const audio = new Audio(withBasePath(file));
   audio.volume = 0.3;
   audio.play().catch((e) => {
     debug.log('push', 'Could not play audio file, falling back to beep:', e);