Add incremental metadata/artwork sync to iPod (iTunes-style)

- content_hash() — SHA1 of first 64KB for matching local↔iPod tracks
- Nano7Database.update_track_metadata() — update DB records only,
  never touch audio files on the iPod
- Nano7Database.find_track_by_content_hash() + find_track_by_metadata()
- _write_databases_from_tracks() extracted from sync_itunescdb,
  supports artwork_overrides parameter
- LibraryCache stores content_hash for cached tracks
- Worker + UI: 'Sync Metadata to iPod' button + context menu item
- _REMOVE_ARTWORK sentinel for explicit artwork removal
- track_info.py: add play_count, rating, last_played, skip_count fields

src/ui/library_tab.py

@@ -6,6 +6,7 @@ Provides the library UI, playback controls, and transfer/conversion workflows.
 
 import os
 import sys
+import time
 import logging
 from typing import List, Dict, Optional, Tuple, Any
 from pathlib import Path
@@ -22,7 +23,7 @@ from PyQt6.QtMultimedia import QMediaPlayer, QAudioOutput
 from track_info import TrackInfo
 from metadata_handler import MetadataHandler
 from ui.metadata_editor import MetadataEditorDialog
-from library_cache import get_library_cache, invalidate_cache_for_path
+from library_cache import get_library_cache, invalidate_cache_for_path, save_library_cache
 from artwork.cache import cover_cache
 from config_loader import ConfigLoader
 from worker import WorkerThread
@@ -74,6 +75,7 @@ class LibraryTab(QWidget):
         self._saved_position_ms: int = 0
         self._saved_playing: bool = False
         self._pending_seek_ms: int = 0
+        self._halfway_passed: set[int] = set()
 
         self._library_toolbar_buttons: list = []
 
@@ -163,9 +165,9 @@ class LibraryTab(QWidget):
         self._setup_library_toolbar(layout)
 
         self.library_table = QTableWidget()
-        self.library_table.setColumnCount(7)
+        self.library_table.setColumnCount(8)
         self.library_table.setHorizontalHeaderLabels(
-            ["#", "Artist", "Title", "Album", "Duration", "Genre", "Size"]
+            ["#", "Artist", "Title", "Album", "Duration", "Genre", "Size", "Plays"]
         )
         self.library_table.setSelectionBehavior(QTableWidget.SelectionBehavior.SelectRows)
         self.library_table.setSelectionMode(QTableWidget.SelectionMode.ExtendedSelection)
@@ -184,6 +186,7 @@ class LibraryTab(QWidget):
         header.setSectionResizeMode(4, QHeaderView.ResizeMode.ResizeToContents)
         header.setSectionResizeMode(5, QHeaderView.ResizeMode.ResizeToContents)
         header.setSectionResizeMode(6, QHeaderView.ResizeMode.ResizeToContents)
+        header.setSectionResizeMode(7, QHeaderView.ResizeMode.ResizeToContents)
 
         layout.addWidget(self.library_table, stretch=1)
 
@@ -281,6 +284,7 @@ class LibraryTab(QWidget):
 
         old_index = self.current_playback_index
         self._clear_playing_row(old_index)
+        self._halfway_passed.discard(old_index)
 
         self.current_playback_index = index
         self.player.setSource(QUrl.fromLocalFile(track_data["path"]))
@@ -407,6 +411,8 @@ class LibraryTab(QWidget):
         if duration > 0 and not self.position_slider.isSliderDown():
             self.position_slider.setValue(int(position / duration * 1000))
         self.time_label_start.setText(self._format_time_ms(position))
+        if duration > 0 and position >= duration * 0.5:
+            self._halfway_passed.add(self.current_playback_index)
 
     def _on_media_duration_changed(self, duration: int):
         self.time_label_end.setText(self._format_time_ms(duration))
@@ -415,9 +421,11 @@ class LibraryTab(QWidget):
 
     def _on_media_status_changed(self, status):
         if status == QMediaPlayer.MediaStatus.EndOfMedia:
+            self._increment_play_count()
             self._stop_eq_animation()
             self._on_next_clicked()
         elif status == QMediaPlayer.MediaStatus.NoMedia:
+            self._halfway_passed.discard(self.current_playback_index)
             self._stop_eq_animation()
             self.play_btn.setText("\u25B6")
             self._is_playing = False
@@ -426,6 +434,34 @@ class LibraryTab(QWidget):
                 self.player.setPosition(self._pending_seek_ms)
                 self._pending_seek_ms = 0
 
+    def _increment_play_count(self):
+        idx = self.current_playback_index
+        if idx not in self._halfway_passed:
+            return
+        if idx < 0 or idx >= self.library_table.rowCount():
+            return
+        data_item = self.library_table.item(idx, 0)
+        if data_item is None:
+            return
+        _is_ready, track_data = data_item.data(Qt.ItemDataRole.UserRole)
+        if not track_data:
+            return
+        path = track_data.get("path", "")
+        if not path:
+            return
+        cache = get_library_cache()
+        entry = cache.get(path)
+        if entry is None:
+            entry = track_data.copy()
+        entry["play_count"] = entry.get("play_count", 0) + 1
+        entry["last_played"] = int(time.time())
+        cache.put(path, entry)
+        save_library_cache()
+        self._halfway_passed.discard(idx)
+        plays_item = self.library_table.item(idx, 7)
+        if plays_item:
+            plays_item.setText(str(entry["play_count"]))
+
     def _start_eq_animation(self):
         if not self._eq_timer or self._eq_running:
             return
@@ -702,6 +738,7 @@ class LibraryTab(QWidget):
                 QTableWidgetItem(duration_str),
                 QTableWidgetItem(track.get("genre", "") or ""),
                 QTableWidgetItem(self._format_size(track["size"])),
+                QTableWidgetItem(str(track.get("play_count", "0") or "0") if is_ready else ""),
             ]
 
             if not is_ready: