refactor: consolidate aria2 process management into state and remove global variables

core/utils/state.py

@@ -1,4 +1,5 @@
 from dataclasses import dataclass
+from typing import Optional, Any
 
 
 @dataclass
@@ -6,6 +7,8 @@ class AppState:
     debug: bool = False
     tracker: str = "rutracker"
     api_url: str = "https://api.michijackson.xyz"
+    aria2process: Optional[Any] = None
+    aria2_threads: int = 4
 
 
 state = AppState()