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/request/__init__.py

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

src/swingmusic/request/artists.py

@@ -0,0 +1,44 @@
+"""
+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
+    ]