enh(doc): improve NTP offset thresholds help

[omercier]

Refs: CTOR-2067

Improve the help for offset thresholds in NTP modes

Type of change

• Patch fixing an issue (non-breaking change)
• New functionality (non-breaking change)
• Functionality enhancement or optimization (non-breaking change)
• Breaking change (patch or feature) that might cause side effects breaking part of the Software
• Doc

Summary by Aikido

Security Issues: 0	Quality Issues: 0	Resolved Issues: 0

⚡ Enhancements

• Added timezone validation and local TZ setting for UPS APC NTP.

📚 Documentation

• Updated NTP help texts to clarify threshold range format.
• Replaced '--ntp-host' mentions with '--ntp-hostname' and examples.
• Normalized NTP capitalization and clarified timezone option wording.
• Bumped copyright headers to '2026-Present' across files.

^{More info}

[omercier]

Relates to #5873