fix(settings): degrade load_features to defaults on PermissionError

load_settings() already catches PermissionError, but load_features() caught only
FileNotFoundError/JSONDecodeError/ValueError. An existing-but-unreadable
data/features.json (e.g. root-owned after a deploy) therefore raised instead of
falling back to DEFAULT_FEATURES, taking down GET /api/auth/features and anything
that reads feature flags. Add PermissionError to the except tuple to match
load_settings().

Adds tests/test_load_features_permission_error.py.

Co-authored-by: Alexandre Teixeira <111787685+alteixeira20@users.noreply.github.com>

src/settings.py

@@ -283,7 +283,7 @@ def load_features() -> dict:
         if not isinstance(saved, dict):
             raise ValueError("features must be an object")
         merged = {**DEFAULT_FEATURES, **saved}
-    except (FileNotFoundError, json.JSONDecodeError, ValueError):
+    except (FileNotFoundError, PermissionError, json.JSONDecodeError, ValueError):
         merged = dict(DEFAULT_FEATURES)
     _features_cache = (now, merged)
     return merged