Sprint 5 : integration et production -- securite, performance, API publique, documentation

Backend: rate limiter, security headers, blockchain cache service avec RPC,
public API (7 endpoints read-only), WebSocket auth + heartbeat, DB connection
pooling, structured logging, health check DB. Frontend: API retry/timeout,
WebSocket auth + heartbeat + typed events, notifications toast, mobile hamburger
+ drawer, error boundary, offline banner, loading skeletons, dashboard enrichi.
Documentation: guides utilisateur complets (demarrage, vote, sanctuaire, FAQ 30+),
guide deploiement, politique securite. 123 tests, 155 fichiers.

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

backend/app/database.py

@@ -3,7 +3,14 @@ from sqlalchemy.orm import DeclarativeBase
 
 from app.config import settings
 
-engine = create_async_engine(settings.DATABASE_URL, echo=settings.DEBUG)
+engine = create_async_engine(
+    settings.DATABASE_URL,
+    echo=settings.ENVIRONMENT == "development",
+    pool_size=settings.DATABASE_POOL_SIZE,
+    max_overflow=settings.DATABASE_MAX_OVERFLOW,
+    pool_pre_ping=True,
+    pool_recycle=3600,
+)
 async_session = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)