feat(nodes): remote sleep/wake — idle detection + wake-page ingress

Agents report per-container net IO at heartbeat; the sleeper measures
idleness from those counters for remote services, removes replicas via
the agent queue, and repoints the domain route at the backend's new
/internal/wake-page endpoint (replacePath + priority-100 route in the
file provider). First hit serves a reloading page and retriggers the
wake reconcile, which recreates replicas and restores real upstreams.

Manual POST /services/:id/sleep also routes remote; local sleep/wake
flow is unchanged.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/api/routes.go

@@ -285,6 +285,7 @@ func SetupRoutes(router *gin.Engine, db *database.DB, redis *database.Redis, cfg
 			// Wake callback for sleep-mode placeholders. Unauthenticated but
 			// non-destructive: it only reconciles the service back to running.
 			public.Any("/internal/wake/:id", handleServiceWake)
+			public.Any("/internal/wake-page/:id", handleServiceWakePage)
 		}
 
 		// Read routes — public browsing. OptionalAuth resolves a session when