fix: resolve ipod_device import conflict with lazy imports

main.py imports our local ipod_device first, which caches it in
sys.modules.  When ipod_nano7_db later tried 'from ipod_device import
ChecksumType', Python returned the cached local module (which lacks
ChecksumType), causing 'ipod_nano7_db not available' and falling back
to simple file copy into wrong /Music/ directory.

Fix: replace top-level iOpenPod imports with lazy _import_iop() helper
that temporarily evicts local ipod_device from sys.modules, adds
/tmp/iOpenPod to sys.path, loads the iOpenPod module, then restores
the path.  All iOpenPod imports now happen inside method bodies only.

src/ipod_nano7_db.py

@@ -20,6 +20,7 @@ Public API preserved for main.py compatibility:
     delete_orphaned_files(paths)   — remove orphan files
 """
 
+import importlib
 import os
 import sys
 import hashlib
@@ -31,25 +32,38 @@ import struct
 import time
 from typing import Any, Optional
 
-os.environ.setdefault("IOPENOD_HOME", "/tmp/iOpenPod")
-_iop = "/tmp/iOpenPod"
-if _iop not in sys.path:
-    sys.path.insert(0, _iop)
-
 from mutagen import File as MutagenFile
 from mutagen.easyid3 import EasyID3
 
-from iTunesDB_Writer.mhit_writer import TrackInfo as IopTrackInfo
+_IOP_ROOT = "/tmp/iOpenPod"
-from iTunesDB_Writer.mhyp_writer import PlaylistInfo
+
-from iTunesDB_Writer import write_itunesdb as iop_write_itunesdb
+
-from SQLiteDB_Writer import write_sqlite_databases
+def _import_iop(module_name: str):
-from ipod_device import (
+    """Import a module from iOpenPod, bypassing any locally-cached conflict.
-    DeviceCapabilities,
+
-    ChecksumType,
+    main.py imports our local ``ipod_device`` first, which caches it in
-    get_firewire_id,
+    ``sys.modules``.  When ipod_nano7_db later tries ``from ipod_device
-    capabilities_for_family_gen,
+    import ChecksumType``, Python returns the cached *local* module
-    get_current_device,
+    (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.
+    """
+    # 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)
+
+    had_iop = _IOP_ROOT in sys.path
+    if not had_iop:
+        sys.path.insert(0, _IOP_ROOT)
+
+    try:
+        return importlib.import_module(module_name)
+    finally:
+        if not had_iop:
+            sys.path.remove(_IOP_ROOT)
+        sys.modules.update(_saved)
 
 logger = logging.getLogger(__name__)
 
@@ -165,9 +179,10 @@ def _read_audio_tags(filepath: str) -> dict[str, Any]:
 
 
 def _scanned_tracks_to_iop(mountpoint: str,
-                           scanned: list[dict]) -> list[IopTrackInfo]:
+                           scanned: list[dict]) -> list:
     """Convert our scanned track dicts to iOpenPod TrackInfo objects."""
-    tracks: list[IopTrackInfo] = []
+    IopTrackInfo = _import_iop("iTunesDB_Writer.mhit_writer").TrackInfo
+    tracks: list = []
     for s in scanned:
         fpath = s["file_path"]
         fname = os.path.basename(fpath)
@@ -467,11 +482,12 @@ class Nano7Database:
         logger.info("Built %d iOpenPod TrackInfo objects", len(tracks))
 
         # 3. Determine capabilities for this device
+        ipod_device = _import_iop("ipod_device")
         capabilities = None
         try:
-            dev = get_current_device()
+            dev = ipod_device.get_current_device()
             if dev and dev.model_family:
-                capabilities = capabilities_for_family_gen(
+                capabilities = ipod_device.capabilities_for_family_gen(
                     dev.model_family, dev.generation or "",
                 )
             if capabilities:
@@ -481,10 +497,11 @@ class Nano7Database:
 
         # 4. Generate and write binary iTunesDB first (to get db_pid)
         try:
-            firewire_id = get_firewire_id(self.mountpoint)
+            firewire_id = ipod_device.get_firewire_id(self.mountpoint)
         except Exception:
             firewire_id = self.firewire_id
 
+        iop_write_itunesdb = _import_iop("iTunesDB_Writer").write_itunesdb
         ok = iop_write_itunesdb(
             self.mountpoint,
             tracks,
@@ -501,8 +518,8 @@ class Nano7Database:
         # 5. Extract db_pid from the binary DB for SQLite cross-reference
         db_pid = 0
         try:
-            from ipod_device import resolve_itdb_path
+            ipod_dev = _import_iop("ipod_device")
-            cdb_path = resolve_itdb_path(self.mountpoint)
+            cdb_path = ipod_dev.resolve_itdb_path(self.mountpoint)
             if cdb_path:
                 with open(cdb_path, "rb") as f:
                     hdr = f.read(0x20)
@@ -514,6 +531,7 @@ class Nano7Database:
 
         # 6. Write SQLite databases (Nano 6G/7G require this)
         try:
+            write_sqlite_databases = _import_iop("SQLiteDB_Writer").write_sqlite_databases
             sqlite_ok = write_sqlite_databases(
                 ipod_path=self.mountpoint,
                 tracks=tracks,
@@ -532,23 +550,26 @@ class Nano7Database:
 
     def _write_empty_databases(self) -> None:
         """Write minimal empty databases when no tracks exist."""
-        empty_tracks: list[IopTrackInfo] = []
+        ipod_device = _import_iop("ipod_device")
+        iop_write_itunesdb = _import_iop("iTunesDB_Writer").write_itunesdb
+        write_sqlite_databases = _import_iop("SQLiteDB_Writer").write_sqlite_databases
+
         try:
-            fwid = get_firewire_id(self.mountpoint)
+            fwid = ipod_device.get_firewire_id(self.mountpoint)
         except Exception:
             fwid = self.firewire_id
         capabilities = None
         try:
-            dev = get_current_device()
+            dev = ipod_device.get_current_device()
             if dev and dev.model_family:
-                capabilities = capabilities_for_family_gen(
+                capabilities = ipod_device.capabilities_for_family_gen(
                     dev.model_family, dev.generation or "")
         except Exception:
             pass
-        iop_write_itunesdb(self.mountpoint, empty_tracks, firewire_id=fwid,
+        iop_write_itunesdb(self.mountpoint, [], firewire_id=fwid,
                            backup=True, capabilities=capabilities)
         write_sqlite_databases(
-            ipod_path=self.mountpoint, tracks=empty_tracks,
+            ipod_path=self.mountpoint, tracks=[],
             master_playlist_name="iPod",
             db_pid=random.getrandbits(64),
             capabilities=capabilities, firewire_id=fwid, backup=True,