Fix Windows release build failure on latest MSVC toolchain

[Copilot]

The Windows release job started failing on windows-latest during flutter build windows. The breakage came from transitive Windows plugins (local_auth_windows, permission_handler_windows) hitting MSVC's new hard error for deprecated <experimental/coroutine> usage.

• Root cause

  • Current GitHub Actions Windows runners ship an MSVC/STL version that rejects deprecated experimental coroutine support used by plugin native code.
  • The later Compress-Archive failure in the job was secondary; the build output was never produced.

• Change

  • Add a top-level Windows compile definition in windows/CMakeLists.txt:
    • _SILENCE_EXPERIMENTAL_COROUTINE_DEPRECATION_WARNINGS
  • This applies to plugin subprojects built through the app's CMake graph, avoiding direct edits to generated plugin files or dependency sources.

• Why here

  • The failing plugins are added as CMake subdirectories from Flutter's generated Windows plugin wiring, so a single definition at the app level propagates to those targets.

# windows/CMakeLists.txt
add_definitions(-DUNICODE -D_UNICODE)
add_compile_definitions(_SILENCE_EXPERIMENTAL_COROUTINE_DEPRECATION_WARNINGS)

[Copilot]

Pull request overview

This PR addresses a Windows release build failure on windows-latest by adding a global Windows CMake compile definition intended to silence MSVC/STL deprecation diagnostics triggered by transitive Flutter Windows plugins.

Changes:

• Add _SILENCE_EXPERIMENTAL_COROUTINE_DEPRECATION_WARNINGS via add_compile_definitions(...) in the top-level Windows CMake configuration.

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