Fix network time sync and mixed-DPI displays

[taocihei]

What changed

• add HTTPS-based UTC calibration with cached correction and 30-minute refresh
• normalize Beijing time conversion against corrected UTC
• enable Per-Monitor V2 awareness and physical-pixel display geometry
• persist target displays by stable device name instead of enumeration index
• fix mixed-DPI positioning, snapping, hot-corner detection, and resolution labels
• bump the application version to 1.3.1

Why

The Windows Time service on the affected machine was unsynchronized and its UTC base was about 15 hours fast. The clock previously trusted that incorrect UTC value, so selecting Beijing time produced the next day's time. Mixed-DPI displays also exposed physical/logical coordinate mismatches and unstable screen numbering.

Impact

• Beijing time remains accurate even when the Windows clock is intentionally shifted or W32Time is unavailable
• cached correction supports offline startup
• multi-monitor placement is stable across restarts and mixed 100%/150% scaling

Validation

• Release build completed with MSBuild and .NET Framework 4.7.2 references
• live UI matched the NIST-derived Beijing time within request latency
• seconds refreshed continuously across exact boundaries
• verified 3840×2160 at 150%, 1920×1080 at 100%, and 2560×1440 at 100%
• verified placement on the 4K/150% monitor and restoration to the selected monitor
• git diff --check passed