feat: add ready audio files (m4a/mp3/aac) to library with structured copy

- Expand Add Files dialog to accept all supported audio formats
- Copy ready files to output_dir/Artist/Album/{track} - Title.ext
- Fallback to output_dir root when metadata is missing
- Handle filename collisions with numeric suffix

src/ui/library_tab.py

@@ -8,6 +8,7 @@ import os
 import sys
 import time
 import logging
+import shutil
 from typing import List, Dict, Optional, Tuple, Any
 from pathlib import Path
 
@@ -753,20 +754,77 @@ class LibraryTab(QWidget):
         self._scan_library(force=True)
 
     def _on_library_add_files(self):
-        source_filter = "Audio Files (*.flac *.wav *.ogg *.opus *.wma *.ape *.aiff *.alac)"
+        all_exts = sorted(SOURCE_EXTS | AUDIO_EXTS)
+        source_filter = f"Audio Files (*{' *'.join(all_exts)})"
         files, _ = QFileDialog.getOpenFileNames(
             self, "Select Audio Files", "", source_filter
         )
-        new_files = []
+        new_source_files = []
+        copied_ready = []
         for f in files:
             ext = os.path.splitext(f)[1].lower()
             if ext in SOURCE_EXTS and os.path.exists(f) and f not in self.library_source_files:
                 self.library_source_files.append(f)
-                new_files.append(f)
+                new_source_files.append(f)
+            elif ext in AUDIO_EXTS and os.path.exists(f):
+                output_dir = self.get_output_dir()
+                if output_dir:
+                    dest = self._copy_to_library(f, output_dir)
+                    if dest:
+                        copied_ready.append(dest)
 
-        if new_files:
+        if new_source_files or copied_ready:
             self._scan_library()
 
+    def _copy_to_library(self, src: str, output_dir: str) -> str:
+        handler = MetadataHandler()
+        ext = os.path.splitext(src)[1].lower()
+        try:
+            info = handler.extract_tags(src)
+            artist = info.artist if info and info.artist else None
+            album = info.album if info and info.album else None
+            title = info.title if info and info.title else None
+            track_num = info.track_number if info else 0
+        except Exception:
+            artist = album = title = None
+            track_num = 0
+
+        if title:
+            safe_title = self._sanitize_filename(title)
+            safe_artist = self._sanitize_filename(artist) if artist else "_Unknown"
+            safe_album = self._sanitize_filename(album) if album else "_Unknown"
+
+            fname = f"{track_num:02d} - {safe_title}{ext}" if track_num > 0 else f"{safe_title}{ext}"
+            dest_dir = os.path.join(output_dir, safe_artist, safe_album)
+        else:
+            fname = os.path.basename(src)
+            dest_dir = output_dir
+
+        os.makedirs(dest_dir, exist_ok=True)
+        dest = os.path.join(dest_dir, fname)
+
+        if os.path.normpath(src) == os.path.normpath(dest):
+            return dest
+        if not os.path.exists(dest):
+            shutil.copy2(src, dest)
+            return dest
+        base, ext = os.path.splitext(fname)
+        for i in range(1, 100):
+            dest = os.path.join(dest_dir, f"{base}_{i}{ext}")
+            if not os.path.exists(dest):
+                shutil.copy2(src, dest)
+                return dest
+        return None
+
+    @staticmethod
+    def _sanitize_filename(filename: str) -> str:
+        invalid_chars = '<>:"/\\|?*'
+        for char in invalid_chars:
+            filename = filename.replace(char, '_')
+        if len(filename) > 100:
+            filename = filename[:97] + '...'
+        return filename.strip()
+
     def _incremental_update_after_edit(self, file_paths: list):
         cache = get_library_cache()
         handler = MetadataHandler()