fix: watchdog su download upgrader (bump v1.9.1)

Prima: se yt-dlp si bloccava nel download di un video (geo-restricted,
YouTube throttle, rete lenta), il for loop su stdout attendeva
indefinitamente e la tab Upgrade si fermava dopo 2-3 brani.

Ora: threading.Timer da 5 min uccide il subprocess se in scaduta.
Al kill il for esce -> codice trova temp_dir vuota -> marca il brano
"download_error" e prosegue col successivo.

core/config.py

@@ -5,7 +5,7 @@ import os
 import sys
 from pathlib import Path
 
-VERSION = "v1.9.0"
+VERSION = "v1.9.1"
 
 
 APP_NAME = "MusicTools"

core/upgrader.py

@@ -13,6 +13,10 @@ from core.paths import find_ytdlp, find_ffmpeg_dir, find_ffprobe, subprocess_fla
 
 AUDIO_EXTENSIONS = {".mp3", ".m4a", ".wav", ".flac"}
 
+# Timeout massimo per singolo download yt-dlp (secondi). Watchdog kill.
+# Serve a evitare hang su video geo-restricted, YouTube throttle o rete lenta.
+_DOWNLOAD_TIMEOUT_SEC = 300
+
 # Flag globale per interruzione
 _stop_event = threading.Event()
 _current_process: Optional[subprocess.Popen] = None
@@ -288,17 +292,43 @@ def upgrade_folder(
                     cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, text=True,
                     **subprocess_flags(),
                 )
+            proc = _current_process
 
-            for line in _current_process.stdout:
+            # Watchdog: kill del subprocess se supera _DOWNLOAD_TIMEOUT_SEC.
+            # Previene hang indefinito su video problematici (geo-block,
+            # YouTube throttle, rete lenta). Alla scadenza il process viene
+            # terminato -> for line esce -> code path "download_error" naturale.
+            def _watchdog_kill():
+                try:
+                    if proc.poll() is None:
+                        proc.terminate()
+                except Exception:
+                    pass
+            watchdog = threading.Timer(_DOWNLOAD_TIMEOUT_SEC, _watchdog_kill)
+            watchdog.daemon = True
+            watchdog.start()
+
+            try:
+                for line in proc.stdout:
                     if is_stopped():
-                    _current_process.terminate()
+                        proc.terminate()
                         return
                     pct_match = re.search(r"(\d+(?:\.\d+)?)%", line)
                     if pct_match and progress_callback:
                         pct = int(float(pct_match.group(1)))
                         progress_callback(processed, total, filepath.name, "downloading", current_kbps, pct)
 
-            _current_process.wait()
+                try:
+                    proc.wait(timeout=10)
+                except subprocess.TimeoutExpired:
+                    proc.kill()
+                    try:
+                        proc.wait(timeout=5)
+                    except subprocess.TimeoutExpired:
+                        pass
+            finally:
+                watchdog.cancel()
+
             with _process_lock:
                 _current_process = None