fix(entrypoint): make /data traversable; hostname gate first (v1.0.0)

Go TempDir bind mounts arrive as 0700; after chown panel:panel, OpenDKIM
could not reach KeyTable and the container crash-looped. chmod 755 /data,
check SELFPOST_HOSTNAME before /data setup, and harden the e2e stand
(restart: no, readiness logs).

Co-Authored-By: Composer <noreply@cursor.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

test/e2e/process_check.go

@@ -45,7 +45,10 @@ func checkSupervisorProcesses(s *stack) error {
 		}
 		return true, nil
 	})
-	return err
+	if err != nil {
+		return fmt.Errorf("%w\n==== selfpost logs ====\n%s", err, s.logs("selfpost"))
+	}
+	return nil
 }
 
 func parseSupervisorStatus(out string) map[string]string {