feat: loading overlay on dashboard, RDP pooled session routing fix

- dashboard.html: overlay div moved before <script> so getElementById works;
  double rAF ensures browser paints spinner before navigation
- main.py: pooled_rdp route fix — session_status now returns /svc/<slug>/
  route and redirect_url for POOL: RDP sessions (was always ready instantly)
- docker-compose.yml: parametrise env vars via .env for easier tuning

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

app/main.py

@@ -2419,7 +2419,13 @@ def session_status(session_id: str, user: User = Depends(require_user), db: Sess
             universal_pool_idx = int(sess.container_id.split(":", 1)[1])
         except Exception:
             universal_pool_idx = None
-    route_path = f"/svc/{service.slug}/" if pooled_web and service else f"/s/{session_id}/"
+    pooled_rdp = bool(sess.container_id and sess.container_id.startswith("POOL:") and service and service.type == ServiceType.RDP)
+    if pooled_web and service:
+        route_path = f"/svc/{service.slug}/"
+    elif pooled_rdp and service:
+        route_path = f"/svc/{service.slug}/"
+    else:
+        route_path = f"/s/{session_id}/"
     if web_pool_idx is not None:
         route_path = f"/w/{web_pool_idx}/"
     if universal_pool_idx is not None:
@@ -2436,7 +2442,7 @@ def session_status(session_id: str, user: User = Depends(require_user), db: Sess
         "message": "Готово, открываем..." if ready else "Запуск сессии...",
         "steps": steps,
     }
-    if pooled_web:
+    if pooled_web or pooled_rdp:
         payload["redirect_url"] = f"/s/{session_id}/view"
     if web_pool_idx is not None:
         payload["redirect_url"] = f"/s/{session_id}/view"