Release CI: drop the retired macos-13 Intel VPN job (arm64-only VPN)

GitHub retired the free macos-13 Intel runner, leaving the intel-vpn job queued
indefinitely. Remove it and build VPN tools arm64-only on the macos-15 runner.
The app remains universal (swift build --arch arm64 --arch x86_64) and runs on
Intel Macs; only the bundled OpenVPN/WireGuard binaries are Apple-Silicon-only.
Universal VPN can be restored later via a paid macos-*-large Intel runner.

Document 2.3 features in README (Wi-Fi manager, popover reorder, mana…

…ged-profile fix)

Prepare NetFluss 2.2.2 release

Prepare NetFluss 2.2.1 release

Apply DNS presets to enabled services

Prepare NetFluss 2.2 release

Prepare 2.1.1 release

Sign privileged helper in release builds

Prepare NetFluss 2.0 release

Prepare 1.12.1 bugfix release