Reorganize repository structure for better organization

- Move backend code to swingmusic/ folder
- Move client applications to root level (swingmusic-android, swingmusic-desktop, swingmusic-webclient)
- Remove intermediate backend/ and clients/ folders
- Update README with new folder structure and setup instructions
- Clean and organized repository layout

src/swingmusic/request/__init__.py

@@ -1,3 +0,0 @@
-"""
-All network requests are defined here.
-"""

src/swingmusic/request/artists.py

@@ -1,44 +0,0 @@
-"""
-Requests related to artists
-"""
-
-import urllib.parse
-
-import requests
-from requests import ConnectionError, HTTPError, ReadTimeout
-
-from swingmusic.models.lastfm import SimilarArtistEntry
-from swingmusic.utils.hashing import create_hash
-
-
-def fetch_similar_artists(name: str):
-    """
-    Fetches similar artists from Last.fm
-    """
-    url = f"https://kerve.last.fm/kerve/similarartists?artist={urllib.parse.quote_plus(name, safe='')}&autocorrect=1&tracks=1&image_size=large&limit=250&format=json"
-
-    try:
-        response = requests.get(url, timeout=10)
-        response.raise_for_status()
-    except (ConnectionError, ReadTimeout, HTTPError):
-        return None
-
-    data = response.json()
-
-    try:
-        artists = data["results"]["artist"]
-    except KeyError:
-        return []
-
-    return [
-        SimilarArtistEntry(
-           **{
-                "artisthash": create_hash(artist["name"]),
-                "name": artist["name"],
-                "weight": artist["weight"],
-                "listeners": int(artist["listeners"]),
-                "scrobbles": int(artist["scrobbles"]),
-            }
-        )
-        for artist in artists
-    ]