feat: persist scaling policies to Postgres

Adds scaling_policies table and wires the autoscaler: upsert on every
SetScalingPolicy (including delete-as-disable), LoadPolicies hydrates
policies + service states at boot. Persist failures are logged, never
fatal — in-memory state stays authoritative.

Verified live: policy written on POST, survives a full backend restart,
service state re-registers at min_replicas. Also gofmt-fixes the
drifted databases.go struct tags.

Authored By: TDvorak <[email protected]>

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

@@ -48,6 +48,12 @@ func SetupRoutes(router *gin.Engine, db *database.DB, redis *database.Redis, cfg
 	}
 	metricsCollector := metrics.NewMetricsCollector(scheduler, metricsStorage)
 	autoScaler := scaling.NewAutoScaler(scheduler, metricsCollector)
+	if db != nil && db.DB != nil {
+		autoScaler.WithPersistence(db.DB)
+		if err := autoScaler.LoadPolicies(context.Background()); err != nil {
+			log.Printf("Failed to restore scaling policies: %v", err)
+		}
+	}
 	haManager := ha.NewHighAvailabilityManager(scheduler, metricsCollector)
 	haAPIManager := NewHAManager(haManager)