feat: Android download page, analysis retry and a collapsible search

- /android is a public page with the latest APK, the server address to copy
  and three install steps; linked from the sign-in screen and the profile menu
- failed audio analysis can be retried from the library page, which also shows
  the most common error; the analyzer no longer burns attempts on files that
  are missing because the disk is not mounted
- the top bar search folds into a round button and slides open on click, "/"
  or Ctrl+K

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

services/recommender/pipu_rec/analysis/worker.py

@@ -20,6 +20,7 @@ log = logging.getLogger(__name__)
 MAX_ATTEMPTS = 3
 MAX_DURATION_S = 15 * 60
 IDLE_SLEEP_S = 10.0
+MISSING_SLEEP_S = 60.0  # файлы пропали целиком — ждём, пока смонтируют диск
 
 
 @dataclass(frozen=True)
@@ -168,6 +169,18 @@ class Worker:
         )
         conn.commit()
 
+    def postpone(self, conn: psycopg.Connection[Any], track_ids: list[str]) -> None:
+        """Файла нет на диске (не смонтирован?) — обратно в очередь, попытка не засчитывается."""
+        conn.execute(
+            """
+            UPDATE analysis_jobs SET status = 'queued', attempts = greatest(attempts - 1, 0),
+                error = 'file not found — is the disk mounted?', updated_at = now()
+            WHERE track_id = ANY(%s::uuid[])
+            """,
+            (track_ids,),
+        )
+        conn.commit()
+
     def requeue_stale(self, conn: psycopg.Connection[Any]) -> None:
         """Задачи, брошенные упавшим воркером, и признаки старой версии анализатора — снова в очередь."""
         conn.execute(
@@ -189,6 +202,16 @@ class Worker:
             self.requeue_stale(conn)
             while True:
                 jobs = self.claim(conn, self.workers * 2)
+                missing = [j for j in jobs if not Path(j.path).exists()]
+                if missing:
+                    self.postpone(conn, [j.track_id for j in missing])
+                    jobs = [j for j in jobs if j not in missing]
+                    if not jobs:
+                        log.warning(
+                            "analysis: %d files not found, waiting — is the disk mounted?", len(missing)
+                        )
+                        time.sleep(MISSING_SLEEP_S)
+                        continue
                 if not jobs:
                     time.sleep(IDLE_SLEEP_S)
                     continue