Add admin panel, WebSocket support, and API versioning

Introduce an admin portal (React + Nginx), WebSocket routing, and
API versioning middleware with `/api/v1/` prefix deprecation.
Add master API key authentication, new Prometheus metrics for AI
token consumption and active WebSockets, and extend S3 config
with a public endpoint URL. Update test paths and fixtures to
align with the new routing structure.

tests/test_versioning.py

@@ -0,0 +1,64 @@
+"""
+Tests pour vérifier le versionnement de l'API (Middleware & router prefix).
+"""
+import pytest
+from httpx import AsyncClient, ASGITransport
+
+from app.main import app as main_app
+
+@pytest.mark.asyncio
+async def test_api_v1_headers():
+    """
+    Vérifie que les requêtes sous /api/v1/ renvoient bien l'entête X-API-Version.
+    """
+    async with AsyncClient(
+        transport=ASGITransport(app=main_app), base_url="http://testserver"
+    ) as client:
+        # On teste une route qui retourne typiquement un 401 ou 422
+        # mais on vérifie juste la présence de l'entête
+        response = await client.get("/api/v1/images/")
+        assert "x-api-version" in response.headers
+        assert response.headers["x-api-version"] == "v1"
+
+@pytest.mark.asyncio
+async def test_non_versioned_routes_no_header():
+    """
+    Vérifie que les requêtes hors /api/v1/ (ex: /health) n'ont pas l'entête.
+    """
+    async with AsyncClient(
+        transport=ASGITransport(app=main_app), base_url="http://testserver"
+    ) as client:
+        response = await client.get("/health")
+        assert response.status_code == 200
+        assert "x-api-version" not in response.headers
+
+@pytest.mark.asyncio
+async def test_sunset_header_if_configured(monkeypatch):
+    """
+    Vérifie que l'entête Sunset est ajouté si la config est présente.
+    """
+    import app.middleware.versioning
+    
+    # Mock settings in the versioning module
+    class MockSettings:
+        API_V1_SUNSET_DATE = "2025-12-31"
+        
+    monkeypatch.setattr(app.middleware.versioning, "settings", MockSettings())
+
+    async with AsyncClient(
+        transport=ASGITransport(app=main_app), base_url="http://testserver"
+    ) as client:
+        response = await client.get("/api/v1/images/")
+        assert "sunset" in response.headers
+        assert response.headers["sunset"] == "2025-12-31"
+
+@pytest.mark.asyncio
+async def test_deprecated_root_paths_return_404():
+    """
+    Vérifie que l'ancienne route /images renvoie bien un 404.
+    """
+    async with AsyncClient(
+        transport=ASGITransport(app=main_app), base_url="http://testserver"
+    ) as client:
+        response = await client.get("/images/")
+        assert response.status_code == 404