chore: initial project setup

Phase 0 — full project scaffold with:
- Backend: FastAPI + SQLAlchemy 2.0 async + Alembic + PostgreSQL 16
- Frontend: React 18 + TypeScript + Vite + Tailwind CSS + shadcn/ui
- Docker Compose (prod + dev override with hot-reload)
- Health endpoint, CORS config, API proxy, env template

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/.prettierrc

@@ -0,0 +1,7 @@
+{
+  "semi": true,
+  "singleQuote": false,
+  "tabWidth": 2,
+  "trailingComma": "all",
+  "plugins": ["prettier-plugin-tailwindcss"]
+}