fix(p8h): restore daemon --super refusal, race-free secret-file check, remaining log escapes

- server_module_gate: refuse client-chosen ownership against the ORIGINAL config
  so an explicit --super is still refused under an operator --no-super veto
  (the veto must not turn a refusal into an accept).
- credentials: open-then-fstat the exact secret inode, require current-user
  ownership and no group/other bits, but continue to allow process-substitution
  FIFOs; removes the stat->fopen TOCTOU.
- file.c preallocate + protocol.c send-string debug logs escape attacker paths.
- usage/RSYNC_COMPAT updated for --old-args no-op and secret-file rules.

src/shared/protocol.c

@@ -430,10 +430,14 @@ static bool protocol_send_str_impl(ProtocolSession* session, const char* data, b
     return false;
   if (!protocol_send_n_data(session, data, size))
     return false;
-  if (redact)
+  if (redact) {
     log_debug_message(LOG_DEBUG_PROTO, "Send String: <redacted>");
-  else
-    log_debug_message(LOG_DEBUG_PROTO, "Send String: %s", data);
+  } else {
+    char* escaped_data = output_escape(data, log_get_8_bit_output());
+    log_debug_message(LOG_DEBUG_PROTO, "Send String: %s",
+                      escaped_data ? escaped_data : "<allocation failed>");
+    free(escaped_data);
+  }
   return true;
 }