feat(rag): consolidate 14 RAG files into clean app/rag/ package facade

feat(x402): vertical slice — Pydantic facade over legacy x402 payment system

feat(scanner): vertical slice — Pydantic facade over legacy 4,109-line scanner

feat(token): vertical slice — pure-Python domain + 5 thin v1 routes

feat(wallet): vertical slice — pure-Python domain + 4 thin v1 routes

feat(alerts): vertical slice — pure-Python domain + thin v1 route