Merge feat/unified-server: server built on quant.h (fixes #77)

SmolLM2-1.7B: garbage → 23 tok/s
Phi-3.5-mini: crash → 6.5 tok/s

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: unamedkr