fix: priority_queue async context methods (async_fix for Python 3.14+). Add test_priority_limiter.py tests for async context manager

src/nsct/providers/priority_queue.py

@@ -116,8 +116,8 @@ class PriorityLimiter:
         self._lock = asyncio.Lock()
         self._semaphore = asyncio.Semaphore(limit)
 
-    def __aenter__(self) -> "PriorityLimiter":
+    async def __aenter__(self) -> "PriorityLimiter":
         return self
 
-    def __aexit__(self, *exc: Any) -> None:
+    async def __aexit__(self, *exc: Any) -> None:
         pass