feat: publish standalone worker

Separate worker packaging and service lifecycle from the control plane.

app/models/region.go

@@ -0,0 +1,20 @@
+package models
+
+import (
+	"rsgit.ru/rsmon/rsmon/app/models/concerns"
+)
+
+// DefaultRegionCode is the historical default region code seeded by
+// Migrate() (see app/models/migrate.go). Centralized here so admin
+// endpoints and check_jobs.go agree on the literal.
+const DefaultRegionCode = "local"
+
+// Region represents a geographic region where distributed workers can run
+type Region struct {
+	concerns.Model
+	Code     string `gorm:"uniqueIndex;size:20;not null" json:"code"` // e.g. "ru-msk", "us-east", "eu-west"
+	Name     string `gorm:"not null" json:"name"`                     // "Moscow, Russia"
+	Enabled  bool   `gorm:"not null;default:true" json:"enabled"`
+	Priority int    `gorm:"not null;default:0" json:"priority"`
+	concerns.Timestamped
+}