feat: add stage 0 foundation

docs/development/local-setup.md

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+# Local Setup
+
+## Prerequisites
+
+- Python 3.12
+- Node.js 22
+- Docker Desktop
+
+## First Run
+
+```bash
+copy .env.example .env
+cd infra
+docker compose --env-file ../.env up --build
+```
+
+Backend:
+
+- API: http://localhost:8000/api/docs
+- Health: http://localhost:8000/api/system/health
+
+Frontend:
+
+- App: http://localhost:5173
+
+## Backend Tests
+
+```bash
+cd backend
+python -m pip install -e ".[dev]"
+pytest -v
+```
+
+## Frontend Checks
+
+```bash
+cd frontend
+npm install
+npm run typecheck
+npm run build
+```

docs/frontend/design-system.md

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+# Frontend Design System
+
+## Principles
+
+- Build product screens from shared tokens and primitives.
+- Keep operational pages dense, quiet, and optimized for repeated use.
+- Use semantic status colors for ticket state, priority, audit, AI, and system feedback.
+
+## Tokens
+
+Theme tokens live in `frontend/src/styles/globals.css` and are exposed through Tailwind in
+`frontend/tailwind.config.ts`.
+
+Core tokens:
+
+- `background`, `foreground`, `surface`, `border`
+- `muted`, `muted-foreground`
+- `primary`, `success`, `warning`, `danger`, `info`, `ai`
+
+## Components
+
+Base UI primitives:
+
+- `Button`
+- `Badge`
+- `Card`, `CardHeader`, `CardContent`
+
+Product components:
+
+- `AppPageHeader`
+- `AppStatusBadge`
+- `AppPriorityBadge`
+
+Preview page:
+
+- `frontend/src/features/design-system/DesignSystemPreview.tsx`