1. prescreener.py: classify_with_deepseek now retries on 429 with
exponential back-off (5s → 10s → 20s → 40s, up to 4 attempts);
same back-off also covers other transient errors.
2. main.py: prescreen batches run sequentially with a 3s gap instead
of asyncio.gather (parallel). Parallel batches caused the second
batch to always hit the 429 rate limit, leaving most domains
unclassified (only the smaller last batch succeeded).
3. index.html: prescreenSelected() now clears this.domains before
calling _fetch() so Alpine re-renders the full table with the
updated niche/type values; also updates the notify hint to mention
the expected 1-2 min wait.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>