fix: _jar_to_dict prefers get_dict() to survive cross-domain cookie conflicts

the preview cookie map still used jar.items(), which raises curl_cffi CookieConflict when
the same cookie name lives on two domains - the blanket except then returned {}, so preview()
silently showed zero cookies in exactly the state ec1a20a adopted get_dict() to survive on
get_cookies. prefer get_dict() when the jar exposes it (hasattr-guarded), fall back to items()
for a plain mapping jar. preview-only; the items() path is unchanged for jars without get_dict.

Signed-off-by: disqualifier <dev@disqualifier.me>

src/aioweb_tls/backends.py

@@ -118,6 +118,10 @@ def _jar_to_dict(session):
     if not jar:
         return {}
     try:
+        # prefer get_dict() where the jar exposes it: items() raises curl_cffi CookieConflict
+        # when the same name lives on two domains, get_dict() flattens instead (mirrors get_cookies)
+        if hasattr(jar, "get_dict"):
+            return jar.get_dict()
         return {k: v for k, v in jar.items()}
     except Exception:
         return {}