fix: preserve HTTP method across retries in spider session

SessionManager.fetch() pops `method` from `_session_kwargs`,
which mutates the original request dict. When the engine retries
a blocked request via request.copy(), the copy no longer has
`method`, so it defaults to GET.

Steps to reproduce:
1. Yield Request(url, method="POST", data=...)
2. Target returns a response that triggers is_blocked()
3. Engine retries via request.copy() → second fetch uses GET

Fix: copy the kwargs dict before popping, so the original
request stays intact.

scrapling/spiders/session.py

@@ -112,10 +112,12 @@ class SessionManager:
                 client = session._client
 
                 if isinstance(client, _ASyncSessionLogic):
+                    kwargs = request._session_kwargs.copy()
+                    method = cast(SUPPORTED_HTTP_METHODS, kwargs.pop("method", "GET"))
                     response = await client._make_request(
-                        method=cast(SUPPORTED_HTTP_METHODS, request._session_kwargs.pop("method", "GET")),
+                        method=method,
                         url=request.url,
-                        **request._session_kwargs,
+                        **kwargs,
                     )
                 else:
                     # Sync session or other types - shouldn't happen in async context