feat: auto-detect iPod connection via QTimer polling + fix AlreadyMounted in _mount_linux

src/device_monitor.py

@@ -0,0 +1,38 @@
+import logging
+from typing import Set
+
+from PyQt6.QtCore import QObject, QTimer, pyqtSignal
+
+from ipod_device import IPodDevice
+
+logger = logging.getLogger(__name__)
+
+
+class DeviceMonitor(QObject):
+
+    state_changed = pyqtSignal(list)
+
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self.timer = QTimer(self)
+        self.timer.timeout.connect(self._poll)
+        self._device_ids: Set[str] = set()
+
+    def start(self, interval_ms: int = 3000):
+        self._device_ids.clear()
+        self._poll()
+        self.timer.start(interval_ms)
+
+    def stop(self):
+        self.timer.stop()
+        self._device_ids.clear()
+
+    def _poll(self):
+        try:
+            devices = IPodDevice().detect_devices()
+            current_ids = {d["id"] for d in devices}
+            if current_ids != self._device_ids:
+                self._device_ids = current_ids
+                self.state_changed.emit(devices)
+        except Exception:
+            logger.exception("DeviceMonitor poll failed")