docs: add next-phase roadmap, milestone design docs, and CLAUDE.md

- roadmap.md: M1 (DB consolidation) -> M2 (React SPA) -> M3 (token/mobile)
- docs/design/: agent-pipeline design docs with atomic tasks for M1-M3
- CLAUDE.md: workflow, doc map, commit conventions, review-notes briefing flow
- .gitignore: ignore local review-notes/

.gitignore

@@ -5,3 +5,4 @@
 __pycache__/
 *.pyc
 data/
+review-notes/