modularize src

+ merge main.py and manage.py
+ move start logic to swingmusic/__main__.py
+ add a run.py on the project root

swingmusic/crons/mixes.py

@@ -0,0 +1,25 @@
+from swingmusic.crons.cron import CronJob
+from swingmusic.lib.recipes.artistmixes import ArtistMixes
+from swingmusic.lib.recipes.because import BecauseYouListened
+
+
+class Mixes(CronJob):
+    """
+    This cron job creates mixes displayed on the homepage.
+    """
+
+    name: str = "mixes"
+    hours: int = 12
+
+    def __init__(self):
+        super().__init__()
+
+    def run(self):
+        """
+        Creates the artist mixes
+        """
+        ArtistMixes()
+
+        # INFO: Because you listened to artist items are generated using
+        # the artist mixes, so run them after the artist mixes are created.
+        BecauseYouListened()