fix: reuse Cloudflare session for site media

tests/test_source_adapters.py

@@ -25,6 +25,7 @@ class FakeResponse:
                 "media": [{"type": "photo", "url": "https://example.test/1.jpg"}],
             }],
             "browser_state": {"cookies": [{"name": "cf_clearance"}]},
+            "browser_user_agent": "Test Browser",
         }
 
 
@@ -69,6 +70,7 @@ class SourceAdapterTests(unittest.IsolatedAsyncioTestCase):
         self.assertEqual(items[0].text, "Title\n\nBody")
         self.assertEqual(items[0].media[0].url, "https://example.test/1.jpg")
         self.assertEqual(state["browser_state"]["cookies"][0]["name"], "cf_clearance")
+        self.assertEqual(state["browser_user_agent"], "Test Browser")
 
     async def test_followed_page_does_not_repeat_title(self) -> None:
         client = SiteParserClient(FollowedPageSession(), "http://worker", "token", "captcha", 30)