- Remove payneteasy-audit (bash wrapper) and scripts/
- Add audit-clickhouse: Spring Boot 3.4, Java 21, clickhouse-jdbc
- Three endpoints: /funnel, /funnel/gates, /hypotheses
- First production data: AR=53.4%, H6=21K chain declined, H4=3DS timeout
- Update .gitignore, .env.example, Makefile, README

Secrets now come only from .env; config.sh fails fast without credentials.
Also fixes Java 21 detection in Makefile, async response parsing, and debug checks.

Co-authored-by: Cursor <cursoragent@cursor.com>