Fix analytics accuracy, tenant isolation, and event-loop blocking.

Fix 429 rate limits and show friendly errors in widget.

Fix catalog short-circuit replaying book intro on skepticism follow-ups.

Fix purchase objections wrongly blocked as off-topic when politics is mentioned.

feat: Phases 1-5 production improvements + 8 bug fixes

Overhaul: Python-first intent (3-tier), hybrid rewriter, improved system prompt, chunk dedup, LRU cache, natural upsell (button-only CTA)

Restructure project for HF Spaces deployment