feat: sprint 1 — auth + CRUD engagements

Ship the first feature end-to-end on the UI: users log in with JWT,
admins manage user accounts, and any authenticated user (per RBAC)
can create, list, view, edit, and delete engagements.

Backend (Flask + SQLAlchemy + SQLite, 63 pytest)
- User / Engagement models, Alembic 0001 initial schema
- argon2 password hashing, JWT bearer (60-min TTL), @login_required
  and @role_required decorators
- 13 API endpoints under /api/*, including last-admin protection on
  DELETE/PATCH user and JSON 404 on unknown /api/* paths
- `flask create-admin` CLI with duplicate / short-password handling

Frontend (React + Vite + Tailwind + TanStack Query, 20 vitest)
- Inter font bundled locally (no CDN), DESIGN.md tokens in Tailwind
- LoginPage / EngagementsList / EngagementForm / EngagementDetail /
  UsersAdmin pages with role-aware UI
- Layout, ProtectedRoute, StatusBadge, FormField, LoadingState,
  ErrorState, EmptyState, Toast + provider
- Axios client: Bearer interceptor, 401 → purge + /login + "Session
  expirée" toast, 403 → "Accès refusé" toast (declarative <Navigate>
  for already-authed users, Fragment-keyed admin user rows)

Deployment
- Single multistage Dockerfile (node:20-alpine → python:3.12-slim)
- docker/entrypoint.sh runs `flask db upgrade` before `flask run`
- Makefile: build/start/stop/restart/update/logs/create-admin/
  update-mitre/test-{backend,frontend,e2e}/clean
- .env.example documenting MIMIC_JWT_SECRET / MIMIC_DB_PATH / MIMIC_PORT
- SQLite at /data/mimic.sqlite on named volume mimic-data

Acceptance suite (Playwright, 36 tests, all 27 ACs)
- e2e/ scaffold with playwright.config + auth/api fixtures
- One spec per user story (us1-bootstrap through us6-deployment)
- Portable via MIMIC_CONTAINER_CMD / MIMIC_BASE_URL (docker or podman)

Docs
- README.md with quick-start and architecture overview
- CHANGELOG.md updated with Sprint 1 deliverables
- pyrightconfig.json so the Python LSP sees backend/.venv and
  resolves the `backend.app.*` absolute imports

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/tests/Toast.test.tsx

@@ -0,0 +1,62 @@
+import { describe, expect, it } from 'vitest';
+import { act, render, screen, waitFor } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { ToastProvider, useToast } from '@/hooks/useToast';
+import { ToastViewport } from '@/components/Toast';
+
+function Pusher() {
+  const { push } = useToast();
+  return (
+    <div>
+      <button onClick={() => push('Session expirée', 'error')}>Push session</button>
+    </div>
+  );
+}
+
+describe('Toast', () => {
+  it('renders pushed toasts and lets the user dismiss them manually', async () => {
+    const user = userEvent.setup();
+    render(
+      <ToastProvider>
+        <Pusher />
+        <ToastViewport />
+      </ToastProvider>,
+    );
+
+    await user.click(screen.getByRole('button', { name: /push session/i }));
+    const toast = await screen.findByTestId('toast');
+    expect(toast).toHaveTextContent('Session expirée');
+    expect(toast).toHaveAttribute('data-kind', 'error');
+
+    await user.click(screen.getByRole('button', { name: /dismiss/i }));
+    await waitFor(() => {
+      expect(screen.queryByTestId('toast')).toBeNull();
+    });
+  });
+
+  it('auto-dismisses after the timeout', async () => {
+    // Override the 4s default by polling the DOM up to 6s. Real timers keep
+    // user-event happy; the toast hook clears itself via setTimeout.
+    const user = userEvent.setup();
+    render(
+      <ToastProvider>
+        <Pusher />
+        <ToastViewport />
+      </ToastProvider>,
+    );
+
+    await user.click(screen.getByRole('button', { name: /push session/i }));
+    expect(await screen.findByTestId('toast')).toBeInTheDocument();
+
+    await waitFor(
+      () => {
+        expect(screen.queryByTestId('toast')).toBeNull();
+      },
+      { timeout: 6000 },
+    );
+    // Quiet act() warning by flushing any pending state.
+    await act(async () => {
+      await Promise.resolve();
+    });
+  }, 10_000);
+});