v0.2.0: server, replay, studio

On top of v0.1.0 headless MVP.

New: local FastAPI server plus SQLite store (serve command, 7 endpoints with paginated events), Cloudflare scaffold (wrangler plus D1 schema plus static demo), time-travel replay in the static demo and in the new React plus Cytoscape Studio (apps/studio, strict TS), request samples with arrival and finish times.

Verify: ruff plus strict mypy clean, 33 pytest green, CI green, golden hash pinned, SLO 840k events in 0.6s on i7-1255U.

Studio build is yours: cd apps/studio, npm install, npm run build.