fix(ci): replace msbuild longbridge.sln with cmake --build for Windows

[hogan-yuan]

Problem

windows-latest runner was upgraded to VS2026 (MSBuild 18.6.3), which generates a different .sln filename than VS2022. The Makefile.toml had longbridge.sln hardcoded, causing:

MSBUILD : error MSB1009: Project file does not exist.
Switch: longbridge.sln

Fix

Replace msbuild longbridge.sln with cmake --build . in c/Makefile.toml and cpp/Makefile.toml. cmake --build delegates to the underlying build system and doesn't depend on the .sln filename.

Before:

[tasks.c.windows]
command = "msbuild"
args = ["longbridge.sln", "-p:Configuration=Debug", "/t:cargo-build_longbridge_c"]

After:

[tasks.c.windows]
command = "cmake"
args = ["--build", ".", "--config", "Debug", "--target", "cargo-build_longbridge_c"]

This change is backward-compatible with VS2022 and works with any cmake generator.