Web player overhaul; iOS random sort, stems-only filter, pooled libraries

Web: live Stem Now status that tracks every queued song (albums too),
right-click menus with Stem Now, Songs and Genres pages, a Stems Only
filter in place of the sidebar section, Random sort, several pooled
Plex servers and libraries, themes plus custom CSS, a reorganised
settings page that loads without a refresh, saved mixes, karaoke and
synced lyrics, stem playlists and offline downloads.

iOS: Random in every sort menu, a Stems Only toggle (sort menu and
Settings), and several music libraries pooled from the signed-in server.
Settings now persists karaoke and speed across launches.

stemd writes a status file that stemserve serves at /api/queue.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/stemserve.py

@@ -15,6 +15,8 @@ Endpoints (all GET unless noted; add ?token=... or X-Stem-Token when TOKEN is se
   /api/peaks?key=<key>&n=<buckets>           per-stem RMS envelopes, 0..1000
   POST /api/prepare?key=<key>&fmt=opus&br=160 start transcodes in the background
   POST /api/stem  {"paths": [...]}           "Stem Now": stemd separates these Plex files next
+  /api/queue                                 Stem Now progress: pending paths, the track in progress,
+                                             tracks done since stemd started, recent failures
   /file/<key>/<file>[?fmt=opus&br=160]       the stem itself, with Range support
   /plex/...                                  proxy to PLEX_URL (needs TOKEN or the Plex token)
   /api/config                                Plex URL and token from PLEX_URL / PLEX_TOKEN, if set
@@ -24,6 +26,7 @@ Endpoints (all GET unless noted; add ?token=... or X-Stem-Token when TOKEN is se
 """
 
 import email.utils
+import glob
 import hashlib
 import json
 import operator
@@ -106,9 +109,10 @@ class Index:
         return self._count
 
     def refresh(self):
+        """Rescans STEMS_DIR. Returns False if another scan was already running."""
         # One scan at a time; callers that lose the race use the previous result.
         if not self._scanning.acquire(blocking=self._at == 0):
-            return
+            return False
         try:
             tracks = []
             for root, dirs, files in os.walk(STEMS_DIR):
@@ -128,6 +132,7 @@ class Index:
                 self._at = time.monotonic()
         finally:
             self._scanning.release()
+        return True
 
 
 def _read_marker(folder, files):
@@ -354,6 +359,8 @@ class Handler(BaseHTTPRequestHandler):
                 return self._prepare(query)
             if path == "/api/stem":
                 return self._stem_now()
+            if path == "/api/queue":
+                return self._queue()
             if path.startswith("/file/"):
                 return self._file(path[len("/file/"):], query)
             return self._error(404, "not found")
@@ -422,6 +429,32 @@ class Handler(BaseHTTPRequestHandler):
             log(f"stem now: {len(paths)} track{'' if len(paths) == 1 else 's'} queued")
         self._send(202, json.dumps({"queued": len(paths)}).encode())
 
+    _seen_done = None
+
+    def _queue(self):
+        """What stemd has left to do, from its request files and the status file it keeps."""
+        pending = []
+        for req in sorted(glob.glob(os.path.join(QUEUE_DIR, "*.json"))):
+            try:
+                with open(req, encoding="utf-8") as f:
+                    paths = json.load(f).get("paths")
+            except (OSError, ValueError, AttributeError):
+                continue
+            if isinstance(paths, list):
+                pending += [p for p in paths if isinstance(p, str)]
+        try:
+            with open(os.path.join(QUEUE_DIR, ".status.json"), encoding="utf-8") as f:
+                st = json.load(f)
+        except (OSError, ValueError):
+            st = {}
+        done = st.get("done", 0)
+        # A track just finished: rescan now so the index the client fetches next includes it.
+        if done != Handler._seen_done and INDEX.refresh():
+            Handler._seen_done = done
+        self._send(200, json.dumps({"pending": pending, "current": st.get("current"), "done": done,
+                                    "failed": st.get("failed", []), "at": st.get("at")}).encode(),
+                   headers={"Cache-Control": "no-store"})
+
     def _file(self, rel, query):
         key, _, fname = rel.rpartition("/")
         src = _resolve(key, fname)