fix(task-base): on_failure logging crashes on reserved LogRecord keys

When a Celery task failed, on_failure passed extra={"args": ..., "kwargs": ...}
to logger.error. Python's logging.makeRecord rejects any extra key that
collides with a built-in LogRecord attribute, and "args" is one (used for
printf formatting). The KeyError raised inside the error handler then
cascaded through Celery's trace.handle_failure, masking the real task
exception entirely.

Rename the keys to task_args / task_kwargs.

Surfaced while debugging why the loyalty welcome email never got sent —
the underlying task was failing, but the on_failure handler crashed before
logging the real cause, leaving nothing in worker logs to investigate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/modules/task_base.py

@@ -113,8 +113,11 @@ class ModuleTask(Task):
             extra={
                 "task_name": self.name,
                 "task_id": task_id,
-                "args": args,
-                "kwargs": kwargs,
+                # NOT "args"/"kwargs" — both clash with reserved LogRecord
+                # attribute names and cause logging.makeRecord to raise
+                # KeyError, which then masks the real task failure.
+                "task_args": args,
+                "task_kwargs": kwargs,
                 "exception": str(exc),
                 "traceback": str(einfo),
             },