ci: add Windows matrix to Android build

[janicduplessis]

Summary

Adds windows-latest to the Android build matrix so we can validate whether #691 is a problem in this library or in the reporter's environment.

The report is a CMake link failure when building react_codegen_safeareacontext.so on Windows with RN 0.82.1 Fabric: every missing symbol is from libc++_shared / libc++abi (std::__ndk1::basic_string, __cxa_*, operator new/delete, vtable for std::exception, …), which suggests the C++ stdlib is not being linked into the codegen library on Windows. Without a Windows machine it's not possible to tell whether this reproduces against our example app or is specific to the reporter's setup.

Both android-build (Paper) and android-build-fabric (Fabric) jobs now run on Ubuntu and Windows. defaults.run.shell: bash is set so ./gradlew works the same way on both runners — GitHub-hosted Windows runners ship Git Bash. fail-fast: false keeps the existing Ubuntu coverage green even if the Windows job is broken.

The example app currently pins react-native@^0.80.1 while the issue is reported against 0.82.1; if the Windows job passes here we'll still need to confirm against 0.82 separately, but a green Windows build on 0.80 + Fabric would already be a strong signal that the codegen CMakeLists is fine and the failure is environmental.

Test Plan

• CI runs the four-cell matrix (Paper/Fabric × Ubuntu/Windows).
• Ubuntu cells should stay green (no behavioural change).
• Windows cells: observe whether they reproduce the link error from Windows build fails with RN 0.82.1 Fabric (C++20 / NDK mismatch) – works on macOS #691, or pass.