[borodino] feat(dispatcher): host priority scoring + RAG context from past attacks

Commit `b9ca2ac`

host_scorer.py: heuristic scoring 0-100 (type, attack_surface, CVEs, threat_score, arch, confidence) — pure Python, no extra deps
rag_context.py: MiniLM + Faiss IndexFlatIP, loads 500 past completed attacks, find_similar() returns top-3 (cosine > 0.5 threshold)
campaign_dispatcher: LIMIT 1→20, picks best scored host, injects rag_context into hints before /attack (fully non-blocking)
Dockerfile.borodino: sentence-transformers + faiss-cpu + scikit-learn added with || true (graceful fallback on Alpine without C compiler)

Co-Authored-By: Claude Sonnet 4.6 noreply@anthropic.com