modularize src

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

swingmusic/models/favorite.py

@@ -0,0 +1,15 @@
+from dataclasses import dataclass
+from typing import Any, Literal
+
+
+@dataclass
+class Favorite:
+    hash: str
+    type: Literal["album", "track", "artist"]
+    timestamp: int
+    userid: int
+    extra: dict[str, Any]
+
+    def __post_init__(self):
+        # remove the type prefix from the hash
+        self.hash = self.hash.replace(f"{self.type}_", "")