modularize src

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

swingmusic/lib/recipes/__init__.py

@@ -0,0 +1,29 @@
+"""
+Recipes are a way to create mixes.
+"""
+
+from abc import ABC, abstractmethod
+from typing import Any, List
+
+class HomepageRoutine(ABC):
+    """
+    A routine creates a row of homepage items.
+    """
+
+    @property
+    @abstractmethod
+    def is_valid(self) -> bool: ...
+
+    def __init__(self) -> None:
+        if not self.is_valid:
+            return
+
+        self.run()
+
+    @abstractmethod
+    def run(self) -> List[Any]:
+        """
+        Creates the homepage items and saves them to the
+        homepage store if self.is_valid is true.
+        """
+        ...