Move backend files to root level for cleaner GitHub display

- Move all backend files from swingmusic/ to root level
- Backend files now display directly on GitHub repository page
- Keep client applications as submodules (swingmusic-android, swingmusic-desktop, swingmusic-webclient)
- Update README to reflect new structure (no cd swingmusic needed)
- Cleaner, more professional GitHub repository layout

Files moved to root:
- src/ (main source code)
- pyproject.toml, requirements.txt, run.py
- swingmusic.spec, uv.lock, version.txt
- services/

Result: GitHub shows backend files directly while maintaining organized structure

src/swingmusic/lib/playlistlib.py

@@ -0,0 +1,171 @@
+"""
+This library contains all the functions related to playlists.
+"""
+import random
+import string
+import logging
+from PIL import Image, ImageSequence
+
+from swingmusic import settings
+from swingmusic.models.track import Track
+from swingmusic.store.albums import AlbumStore
+from swingmusic.store.tracks import TrackStore
+
+logger = logging.getLogger(__name__)
+
+def create_thumbnail(image: Image, img_name: str) -> str:
+    """
+    Creates a 250 px high thumbnail from the Image.
+    It will keep the aspect ratio.
+
+    Images are saved in the playlist-img path
+
+    :param image: Image object.
+    :param img_name: Name of image.
+    :return: Filename of image.
+    """
+
+    aspect_ratio = image.width / image.height
+    new_w = round(250 * aspect_ratio)
+    thumb = image.resize((new_w, 250), Image.Resampling.LANCZOS)
+
+    thumb_filename = "thumb_" + img_name
+    thumb_path = settings.Paths().playlist_img_path / thumb_filename
+
+    thumb.save(thumb_path, "webp")
+
+    return thumb_filename
+
+
+def create_gif_thumbnail(image: Image, img_name: str):
+    """
+    Creates a 250 px high thumbnail from the provided GIF.
+    Keeps the aspect ratio.
+
+    Images are saved in the playlist-img path
+
+    :param image: Image object.
+    :param img_name: Name of image.
+    :return: Filename of image.
+    """
+    thumb_name = "thumb_" + img_name
+    thumb_path = settings.Paths().playlist_img_path / thumb_name
+
+    frames = []
+    for frame in ImageSequence.Iterator(image):
+        aspect_ratio = frame.width / frame.height
+        new_w = round(250 * aspect_ratio)
+        thumb = frame.resize((new_w, 250), Image.Resampling.LANCZOS)
+
+        frames.append(thumb)
+
+    frames[0].save(thumb_path, save_all=True, append_images=frames[1:])
+
+    return thumb_name
+
+
+def save_p_image(img: Image, pid: int, content_type: str = None, filename: str = None) -> str:
+    """
+    Saves a playlist banner image and returns the filepath.
+    """
+    # img = Image.open(file)
+
+    random_str = "".join(random.choices(string.ascii_letters + string.digits, k=5))
+
+    if not filename:
+        filename = str(pid) + str(random_str) + ".webp"
+
+    full_img_path = settings.Paths().playlist_img_path / filename
+
+    if content_type == "image/gif":
+        frames = []
+
+        for frame in ImageSequence.Iterator(img):
+            frames.append(frame.copy())
+
+        frames[0].save(full_img_path, save_all=True, append_images=frames[1:])
+        create_gif_thumbnail(img, img_path=filename)
+
+        return filename
+
+    img.save(full_img_path, "webp")
+    create_thumbnail(img, img_name=filename)
+
+    return filename
+
+
+def duplicate_images(images: list):
+    if len(images) == 1:
+        images *= 4
+    elif len(images) == 2:
+        images += list(reversed(images))
+    elif len(images) == 3:
+        images = images + images[:1]
+
+    return images
+
+# TODO: mutable var in param.
+def get_first_4_images(
+        tracks: list[Track] = [],
+        trackhashes: list[str] = []
+) -> list[dict["str", str]]:
+    """
+    Returns images of the first 4 albums that appear in the track list.
+
+    When tracks are not passed, trackhashes need to be passed.
+    Tracks are then resolved from the store.
+    """
+    if len(trackhashes) > 0:
+        tracks = TrackStore.get_tracks_by_trackhashes(trackhashes)
+
+    albums = []
+
+    for track in tracks:
+        if track.albumhash not in albums:
+            albums.append(track.albumhash)
+
+            if len(albums) == 4:
+                break
+
+    albums = AlbumStore.get_albums_by_hashes(albums)
+    images = [
+        {
+            "image": album.image,
+            "color": album.color,
+        }
+        for album in albums
+    ]
+
+    if len(images) == 4:
+        return images
+
+    return duplicate_images(images)
+
+
+def cleanup_playlist_images() -> None:
+    """
+    Deletes all unlinked files in playlist-img folder.
+    All files not present in the PlaylistTable will get deleted
+    """
+    # Import here to avoid circular import
+    from swingmusic.db.userdata import PlaylistTable
+
+    playlists = PlaylistTable.get_all()
+    linked_images = {p.image for p in playlists if p.image and p.image != "None"}
+
+    playlist_dir = settings.Paths().playlist_img_path
+
+    # Find unlinked images (including thumbnails)
+    for file in playlist_dir.iterdir():
+        if not file.isfile:
+            continue
+
+        name = file.name # not stem. PlaylistTable saves with extension
+        if file not in linked_images:
+            if name.removeprefix("thumb_") not in linked_images:
+                continue
+
+            try:
+                file.unlink(missing_ok=True)
+            except OSError as e:
+                logger.exception("could not delete file", exc_info=e)