Add phone playback reporting and pause sharing to the API

Phones that read system media sessions report playback themselves:
- POST /me/devices issues a per-phone token that can only call
  POST /devices/now-playing; revocable, hashed at rest, 10 per user
- Reports name the app ("via Spotify"); unknown apps use the OS label
- Push-reported playback expires after 9 minutes of silence, since
  phones send a heartbeat every 4 minutes while playing

Users can pause sharing (PUT /me/sharing: 1h, 8h, indefinitely). While
paused, connections aren't polled, phone reports are dropped, nothing is
added to history, and the current track switches to "played … ago".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MzFywujuH9TiuXbr9vjoX8

apps/api/test/helpers.ts

@@ -17,7 +17,7 @@ function assertTestTargets() {
 
 export async function resetState() {
   assertTestTargets();
-  await sql`truncate users, tracks, track_links, sessions, follows, connections, now_playing, featured_songs, listens restart identity cascade`;
+  await sql`truncate users, tracks, track_links, sessions, follows, connections, now_playing, featured_songs, listens, devices restart identity cascade`;
   await redis.flushdb();
 }