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.

app/metrics.py

@@ -9,12 +9,20 @@ from prometheus_client import Counter, Histogram, Gauge
 hub_images_uploaded = Counter(
     "hub_images_uploaded_total",
     "Nombre total d'images uploadées",
-    ["client_plan"],
+    ["client_id"],
 )
 
 hub_images_deleted = Counter(
     "hub_images_deleted_total",
     "Nombre total d'images supprimées",
+    ["client_id"],
+)
+
+# ── AI ────────────────────────────────────────────────────────
+hub_ai_tokens_consumed = Counter(
+    "hub_ai_tokens_consumed_total",
+    "Nombre total de tokens consommés",
+    ["client_id", "model"],
 )
 
 # ── Pipeline ──────────────────────────────────────────────────
@@ -44,6 +52,12 @@ hub_storage_used_bytes = Gauge(
     ["client_id"],
 )
 
+# ── WebSockets ────────────────────────────────────────────────
+hub_active_websockets = Gauge(
+    "hub_active_websockets",
+    "Nombre de connexions WebSocket actives",
+)
+
 # ── ARQ ───────────────────────────────────────────────────────
 hub_arq_jobs_enqueued = Counter(
     "hub_arq_jobs_enqueued_total",