Merge PR #1035: release per-download status_queue proxy on close to fix fd leak (#485)

Wraps Download.close() in try/finally and nulls self.status_queue so the
per-download manager.Queue() proxy is released once the completed Download is
retained in the done list. Previously every finished download permanently
pinned one Manager-process connection, accumulating file descriptors until
the instance hit 'too many open files' and self-terminated (#485, #980).

Co-authored-by: Matt Van Horn <mvanhorn@users.noreply.github.com>

app/ytdl.py

@@ -787,8 +787,11 @@ class Download:
 
     def close(self):
         log.info(f"Closing download process for: {self.info.title}")
-        if self.started():
-            self.proc.close()
+        try:
+            if self.started():
+                self.proc.close()
+        finally:
+            self.status_queue = None
 
     def running(self):
         try: