Auth : mode prototype factice en prod + fix test DB manquante

- Login : panneau proto-mode en avant quand DEMO_MODE actif (profils API)
  masque le formulaire extension-required ; note trustWallet à venir
- auth.ts : TODO trustWallet avec protocole postMessage prévu
- routers/auth.py : TODO trustWallet au point de vérification signature
- test_middleware : fixture _create_tables (autouse) — ASGITransport ne
  déclenche pas le lifespan, init_db() ne tournait pas → duniter_identities
  introuvable au verify ; 224/224 passent

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

backend/app/tests/test_middleware.py

@@ -14,8 +14,21 @@ from __future__ import annotations
 import pytest
 from httpx import ASGITransport, AsyncClient
 
+import app.models  # noqa: F401 — registers all models with Base.metadata before create_all
+from app.database import init_db
 from app.main import app
 
+
+@pytest.fixture(scope="module", autouse=True)
+async def _create_tables():
+    """Create DB tables once for this module.
+
+    ASGITransport does not trigger the FastAPI lifespan, so init_db() would
+    never run. Tests that hit endpoints backed by the DB need the tables to
+    exist beforehand.
+    """
+    await init_db()
+
 ORIGIN = "http://localhost:3002"
 CHALLENGE_URL = "/api/v1/auth/challenge"
 VERIFY_URL = "/api/v1/auth/verify"