feat: add controller_url to hub reports (v0.16.1)

Controller now includes its external URL in periodic hub reports so the
hub can trigger self-updates remotely via the /api/selfupdate/update endpoint.

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

controller/internal/report/builder.go

@@ -1,6 +1,7 @@
 package report
 
 import (
+	"fmt"
 	"strconv"
 	"strings"
 	"time"
@@ -33,6 +34,11 @@ func BuildReport(
 		Timestamp:         time.Now().UTC(),
 	}
 
+	// Controller URL for hub callbacks (self-update trigger, etc.)
+	if cfg.Customer.Domain != "" {
+		r.ControllerURL = fmt.Sprintf("https://felhom.%s", cfg.Customer.Domain)
+	}
+
 	// System info
 	staticInfo := metrics.GetStaticInfo()
 	hddPath := cfg.Paths.HDDPath