Surface real wardrobe API failures instead of a generic empty message

A non-OK response (auth, rate limit, etc.) was being silently treated
the same as a genuinely empty closet - both showed "no listings
found," with no way to tell which actually happened. Now a failed
request throws with the real HTTP status so the existing top-level
alert shows something actionable instead of a guess.

Verified with a deliberately-bogus user ID: the API itself returns a
clean 200 with total_entries: 0 for a real "nothing here" case, so
that path still correctly shows the empty-closet message - this fix
only changes behavior for genuine request failures.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>