fix: use sync context manager for structlog bound_contextvars

bound_contextvars() returns a sync _GeneratorContextManager, not async.
Using `async with` caused TypeError crashing all web API requests.

app/middlewares/context_binding.py

@@ -23,5 +23,5 @@ class ContextVarsMiddleware(BaseMiddleware):
             ctx['username'] = event.from_user.username or ''
         if hasattr(event, 'chat') and event.chat:
             ctx['chat_id'] = event.chat.id
-        async with bound_contextvars(**ctx):
+        with bound_contextvars(**ctx):
             return await handler(event, data)

app/webapi/middleware.py

@@ -17,7 +17,7 @@ class RequestLoggingMiddleware(BaseHTTPMiddleware):
     """Логирование входящих запросов в административный API."""
 
     async def dispatch(self, request: Request, call_next: RequestResponseEndpoint) -> Response:
-        async with bound_contextvars(http_method=request.method, http_path=request.url.path):
+        with bound_contextvars(http_method=request.method, http_path=request.url.path):
             start = monotonic()
             response: Response | None = None
             try: