Fix Accept-Language q parsing in locale resolver

lobby/i18n.py

@@ -34,14 +34,27 @@ def lobby_i18n_error_messages() -> dict:
     return lobby_i18n_catalog().get("backend", {}).get("errors", {})
 
 
+def _quality_value(language_candidate: str) -> float | None:
+    for parameter in language_candidate.split(";")[1:]:
+        key, separator, value = parameter.partition("=")
+        if separator and key.strip().lower() == "q":
+            try:
+                return float(value.strip())
+            except ValueError:
+                return None
+    return None
+
+
 def resolve_locale(request: HttpRequest) -> str:
     default_locale, supported_locales = i18n_locale_config()
 
     accept_language = request.META.get("HTTP_ACCEPT_LANGUAGE") or ""
     for candidate in accept_language.split(","):
-        tag, _sep, quality = candidate.partition(";")
-        if "q=0" in quality.replace(" ", ""):
+        quality = _quality_value(candidate)
+        if quality is not None and quality <= 0:
             continue
+
+        tag = candidate.split(";", 1)[0]
         normalized = tag.strip().replace("_", "-").split("-", 1)[0].lower()
         if normalized in supported_locales:
             return normalized