fix: address code review findings (pass 1)

Claude-Session: https://claude.ai/code/session_01M9neheZZEe3sVpDi2S3zT4

Author: antosubash

modules/background_tasks/background_tasks/worker_settings.py

@@ -41,12 +41,14 @@ def settings_for[T: BaseSettings](
     with _lock:
         hit = _cache.get(key)
         if hit is not None and ttl > 0 and now - hit[0] < ttl:
-            return cast(T, hit[1])
+            # A copy: BaseSettings is mutable, so one task editing its settings
+            # must not change what the next task in this process sees.
+            return cast(T, hit[1]).model_copy(deep=True)
     with sync_session() as session:
         value = hydrate_settings_sync(cls, session, package)
     with _lock:
         _cache[key] = (now, value)
-    return value
+    return value.model_copy(deep=True)
 
 
 def clear_settings_cache() -> None:

modules/settings/settings/store.py

@@ -60,7 +60,7 @@ def get_overrides_sync(session: Session, package: str) -> dict[str, tuple[str, s
         Setting.scope_id == SYSTEM_SCOPE_ID,
         Setting.key.startswith(f"{package}.", autoescape=True),
     )
-    return package_overrides(((k, v, t) for k, v, t in session.execute(stmt)), package)
+    return package_overrides(session.execute(stmt).tuples(), package)
 
 
 class SettingsStore: