Release v1.0.5

Description:

• Fast date conversion paths (timestamp <-> calendar) with legacy fallbacks + benchmarks
• New DateTime value type (fixed UTC offset): parsing/formatting/arithmetic
• ISO week-date conversions + parsing/formatting
• Astronomy helpers (OA date, JD/MJD/JDN) + MoonPhase improvements
• NTP: POSIX client + pools, offline testing paths, unified realtime_us precision
• Header split into modules while preserving umbrella include + alias coverage across C++11/14/17
• Workday boundary helpers + docs + expanded conversion coverage tests
• US time zone helpers: ET/NY and CT/Chicago -> UTC with DST rules