docs: improve Caddyfile header and note about misconfigured caddy service, minor docs update

internal/machine/caddyconfig/caddyfile.go

@@ -12,14 +12,16 @@ import (
 	"strconv"
 	"strings"
 	"text/template"
+	"time"
 
 	"github.com/psviderski/uncloud/internal/machine/store"
 	"github.com/psviderski/uncloud/pkg/api"
 )
 
 const (
-	caddyfileHeader = `# This file is autogenerated by Uncloud based on the configuration of running services.
-# Do not edit manually. Any manual changes will be overwritten on the next update.
+	caddyfileHeaderFmt = `# Caddyfile autogenerated by Uncloud (DO NOT EDIT): %s
+# Automatically updated on service or health status changes.
+# Docs: https://uncloud.run/docs/concepts/ingress/overview
 `
 	caddyfileTemplate = `# Health check endpoint to verify Caddy reachability on this machine.
 http:// {
@@ -56,7 +58,9 @@ https://{{$hostname}} {
 }{{end}}
 `
 	caddyfileUnavailabeFooter = `# NOTE: User-defined configs for services were skipped because Caddy is not running on this machine
-#       or the latest generated config is invalid. Please check the Caddy logs if it's running.
+#       (not accessible via the shared admin socket /run/uncloud/caddy/admin.sock) or the latest
+#       generated config is invalid. Please check the service 'caddy' is running (uc inspect caddy)
+#       and its logs for more details (uc logs caddy).
 `
 )
 
@@ -120,6 +124,7 @@ func (g *CaddyfileGenerator) Generate(
 		return "", fmt.Errorf("generate base Caddyfile from service ports: %w", err)
 	}
 
+	caddyfileHeader := fmt.Sprintf(caddyfileHeaderFmt, time.Now().UTC().Format(time.RFC3339))
 	if !includeCustom {
 		return fmt.Sprintf("%s\n%s\n%s", caddyfileHeader, caddyfile, caddyfileUnavailabeFooter), nil
 	}