fix: robust iOpenPod imports and sync error handling

_import_iop() now permanently evicts local ipod_device from sys.modules
on first call (instead of restoring it), caches all iOpenPod modules,
and avoids the spurious ModuleNotFoundError cascade on rapid calls.

sync_itunescdb() wrapped in try/except — no longer propagates
import/sync errors to add_track() callers.

ipod_device.py fallback no longer duplicates files to /Music/ when
add_track() already copied them to F00/.

src/ipod_device.py

@@ -543,9 +543,10 @@ class IPodDevice:
             except ImportError:
                 self.logger.warning("ipod_nano7_db not available, using simple file copy")
             except Exception as e:
-                self.logger.error(f"Nano7 database transfer failed: {e}, falling back to simple copy")
+                self.logger.error(f"Nano7 database transfer failed: {e}")
+                return False  # Don't fall back — file was already copied to F00/
             
-            # Fallback: simple file copy (won't show in iPod interface)
+            # Fallback: simple file copy — only on ImportError
             if relative_path:
                 dest_dir = os.path.join(self.mount_point, relative_path)
             else:

src/ipod_nano7_db.py

@@ -36,34 +36,43 @@ from mutagen import File as MutagenFile
 from mutagen.easyid3 import EasyID3
 
 _IOP_ROOT = "/tmp/iOpenPod"
+_IOP_CACHE: dict[str, Any] = {}
+_IOP_READY = False
 
 
 def _import_iop(module_name: str):
-    """Import a module from iOpenPod, bypassing any locally-cached conflict.
+    """Import a module from iOpenPod, evicting our local ipod_device once.
 
-    main.py imports our local ``ipod_device`` first, which caches it in
-    ``sys.modules``.  When ipod_nano7_db later tries ``from ipod_device
-    import ChecksumType``, Python returns the cached *local* module
-    (which lacks ChecksumType).  This helper temporarily evicts the
-    conflicting local modules, adds the iOpenPod root to sys.path, loads
-    the requested module from there, then restores the path.
+    main.py imports our local ``ipod_device`` early, caching it in
+    ``sys.modules``.  On the FIRST call here we permanently evict the
+    local module so iOpenPod's ``ipod_device`` takes its place in
+    ``sys.modules``.  Our local classes (IPodDevice) were already
+    bound by ``from ipod_device import IPodDevice`` in main.py before
+    the eviction, so they stay alive through their own references.
+
+    Subsequent calls are served from a simple module cache.
     """
-    # Modules that may be cached as our local copies and need eviction.
-    _conflicting = {"ipod_device"}
-    _saved = {}
-    for name in _conflicting & set(sys.modules):
-        _saved[name] = sys.modules.pop(name)
+    global _IOP_READY
+    if module_name in _IOP_CACHE:
+        return _IOP_CACHE[module_name]
+
+    if not _IOP_READY:
+        # Evict local shadows ONCE so iOpenPod modules resolve correctly.
+        sys.modules.pop("ipod_device", None)
+        _IOP_READY = True
+        logger.debug("iOpenPod boot: evicted local ipod_device")
 
     had_iop = _IOP_ROOT in sys.path
     if not had_iop:
         sys.path.insert(0, _IOP_ROOT)
-
     try:
-        return importlib.import_module(module_name)
+        mod = importlib.import_module(module_name)
     finally:
         if not had_iop:
             sys.path.remove(_IOP_ROOT)
-        sys.modules.update(_saved)
+
+    _IOP_CACHE[module_name] = mod
+    return mod
 
 logger = logging.getLogger(__name__)
 
@@ -463,12 +472,13 @@ class Nano7Database:
     # ── sync: regenerate everything via iOpenPod ──────────────────────
 
     def sync_itunescdb(self) -> None:
-        """Regenerate ALL databases using iOpenPod's writers.
+        """Regenerate ALL databases using iOpenPod's writers."""
+        try:
+            self._sync_itunescdb_impl()
+        except Exception as e:
+            logger.exception("iTunesDB sync failed: %s", e)
 
-        Scans all audio files on iPod, builds correct TrackInfo list,
-        writes SQLite databases (Library/Locations/Dynamic/Extras/Genius),
-        writes binary iTunesDB, writes iTunesCDB.ext and Locations.cbk.
-        """
+    def _sync_itunescdb_impl(self) -> None:
         # 1. Scan all audio files on iPod
         scanned = self._scan_ipod_files()
         if not scanned: