Polish routing comments and align live regression tests

Fix intent regressions and improve order extraction

fix: handle non-dict JSON bodies (500), add patterns for spaCy mismatches

feat: switch intent engine to spaCy semantic similarity

fix: graceful AI fallback + add missing intent patterns

fix: intent matching, input handling, configurable rate limit

fix: product lookup for bare queries like 'products' and 'electronics'

refactor: reorganize into chatbot/ application package