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_ai_extended.py

@@ -20,7 +20,7 @@ async def test_ai_summarize(async_client: AsyncClient, client_a, auth_headers_a)
          patch("app.routers.ai.settings.AI_ENABLED", True):
         
         payload = {"url": "https://example.com", "language": "français"}
-        response = await async_client.post("/ai/summarize", json=payload, headers=auth_headers_a)
+        response = await async_client.post("/api/v1/ai/summarize", json=payload, headers=auth_headers_a)
         
         assert response.status_code == 200
         data = response.json()
@@ -42,7 +42,7 @@ async def test_ai_draft_task(async_client: AsyncClient, client_a, auth_headers_a
          patch("app.routers.ai.settings.AI_ENABLED", True):
         
         payload = {"description": "Fix bug", "context": "Backend project"}
-        response = await async_client.post("/ai/draft-task", json=payload, headers=auth_headers_a)
+        response = await async_client.post("/api/v1/ai/draft-task", json=payload, headers=auth_headers_a)
         
         assert response.status_code == 200
         data = response.json()
@@ -52,6 +52,6 @@ async def test_ai_draft_task(async_client: AsyncClient, client_a, auth_headers_a
 @pytest.mark.asyncio
 async def test_ai_disabled(async_client: AsyncClient, client_a, auth_headers_a):
     with patch("app.routers.ai.settings.AI_ENABLED", False):
-        response = await async_client.post("/ai/draft-task", json={"description": "test"}, headers=auth_headers_a)
+        response = await async_client.post("/api/v1/ai/draft-task", json={"description": "test"}, headers=auth_headers_a)
         assert response.status_code == 503
         assert response.json()["detail"] == "AI désactivée"