feat: publish standalone worker

Separate worker packaging and service lifecycle from the control plane.

app/models/server_health_ticker.go

@@ -0,0 +1,43 @@
+package models
+
+import (
+	"context"
+	"log"
+	"sync"
+	"time"
+)
+
+// HealthTickInterval is exported so focused tests can exercise the same
+// lifecycle with a short interval.
+var HealthTickInterval = time.Minute
+
+var serverHealthTickerOnce sync.Once
+
+// StartServerHealthTicker periodically refreshes derived server health. The
+// first production tick is delayed to keep CLI migration paths side-effect
+// free; assignment/pause paths recompute synchronously.
+func StartServerHealthTicker(parent context.Context) {
+	serverHealthTickerOnce.Do(func() {
+		go func() {
+			ticker := time.NewTicker(HealthTickInterval)
+			defer ticker.Stop()
+			for {
+				select {
+				case <-parent.Done():
+					return
+				case <-ticker.C:
+					var ids []int64
+					if err := DB().Model(&Server{}).Pluck("id", &ids).Error; err != nil {
+						log.Printf("server health: list: %v", err)
+						continue
+					}
+					for _, id := range ids {
+						if err := HealthForServer(id); err != nil {
+							log.Printf("server health %d: %v", id, err)
+						}
+					}
+				}
+			}
+		}()
+	})
+}