Populate syslog timestamp field when time is available

[BlinkDynamo]

Fixes #7609

Changed syslog messages from always using NILVALUE for the TIMESTAMP field. Now uses RFC5424 UTC timestamp format when a valid time is available from RTC. Falls back to NILVALUE if no valid time is available.

🤝 Attestations

• I have tested that my proposed changes behave as described.
• I have tested that my proposed changes do not cause any obvious regressions on the following devices:
  • Heltec (Lora32) V3
  • LilyGo T-Deck
  • LilyGo T-Beam
  • RAK WisBlock 4631
  • Seeed Studio T-1000E tracker card
  • Other (please specify below)

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[Copilot]

Pull Request Overview

This PR enhances syslog messages by populating the timestamp field with RFC5424 UTC timestamps when valid time is available from the RTC, instead of always using NILVALUE ("-").

Key changes:

• Added RTC time retrieval to check if valid time is available
• Implemented RFC5424-compliant UTC timestamp formatting (YYYY-MM-DDTHH:MM:SSZ)
• Falls back to NILVALUE when no valid time exists

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[Copilot]

The gmtime() function can return NULL if the time value is invalid. This could lead to a null pointer dereference when accessing time_info->tm_year. Add a null check before using the returned pointer.

struct tm *time_info = gmtime(&timestamp);
if (time_info != NULL) {
    char timestamp_buffer[21];
    snprintf(timestamp_buffer, sizeof(timestamp_buffer), "%04d-%02d-%02dT%02d:%02d:%02dZ",
             time_info->tm_year + 1900, time_info->tm_mon + 1, time_info->tm_mday,
             time_info->tm_hour, time_info->tm_min, time_info->tm_sec);
    this->_client->print(timestamp_buffer);
} else {
    this->_client->print(SYSLOG_NILVALUE);
}

Suggested change

	char timestamp_buffer[21];
	snprintf(timestamp_buffer, sizeof(timestamp_buffer), "%04d-%02d-%02dT%02d:%02d:%02dZ",
	time_info->tm_year + 1900, time_info->tm_mon + 1, time_info->tm_mday,
	time_info->tm_hour, time_info->tm_min, time_info->tm_sec);
	this->_client->print(timestamp_buffer);
	} else {
	this->_client->print(SYSLOG_NILVALUE);
	if (time_info != NULL) {
	char timestamp_buffer[21];
	snprintf(timestamp_buffer, sizeof(timestamp_buffer), "%04d-%02d-%02dT%02d:%02d:%02dZ",
	time_info->tm_year + 1900, time_info->tm_mon + 1, time_info->tm_mday,
	time_info->tm_hour, time_info->tm_min, time_info->tm_sec);
	this->_client->print(timestamp_buffer);
	} else {
	this->_client->print(SYSLOG_NILVALUE);
	}

[Copilot]

The RTCQualityDevice enum value should be qualified with the RTCQuality:: namespace. Based on other usages in the codebase (e.g., in RedirectablePrint.cpp, NMEAWPL.cpp), this should be RTCQuality::RTCQualityDevice.

uint32_t timestamp_sec = getValidTime(RTCQuality::RTCQualityDevice, false);

Suggested change

	uint32_t timestamp_sec = getValidTime(RTCQualityDevice, false);
	uint32_t timestamp_sec = getValidTime(RTCQuality::RTCQualityDevice, false);