Standalone binaries (embed) and static builds for Windows

Describe your feature request

Is your feature request related to a problem? Please describe.
Since #2119 (v1.12), FrankenPHP runs natively on Windows, but standalone app binaries (embed) and static builds remain Linux/macOS only: the frankenphp SAPI of static-php-cli isn't available on Windows, and build-static.sh is a Bash script. Distributing a self-contained .exe (app + PHP + Caddy) is currently impossible.

Describe the solution you'd like
Support creating standalone Windows binaries:

• add Windows support to the frankenphp SAPI in static-php-cli, which already builds static PHP with MSVC on Windows for its cli and micro SAPIs;
• provide a Windows counterpart to build-static.sh (e.g. PowerShell). The Go side (embedding the app as a tarball via go:embed) should work on Windows as-is now that FrankenPHP compiles there with Clang against MSVC-built PHP (Go 1.26).

Describe alternatives you've considered

• Building Linux binaries from Windows via Docker or WSL (works today);
• Shipping the Windows release archive (frankenphp.exe + official PHP binaries) next to the app, which is not a single binary.

Related docs PRs: #2500, #2501.

Update: static-php-cli main (v3, unreleased) already ships a Windows build stage for the frankenphp target, so the remaining work is mostly on the FrankenPHP side (build script, docs, CI).

Start with build-static.sh and the existing embed and static documentation to map the current Linux/macOS flow. Then identify the Windows build and CI entry points; done means a Windows counterpart can produce a self-contained .exe, with the relevant docs and CI coverage updated.