Adds a CI step to build and run a sample application that validates the installed PROJ library works correctly. The sample performs a WGS84→UTM transformation and is packaged as a second artifact.

Changes

• sample_app/main.cpp - C++ application demonstrating coordinate transformation (Berlin: WGS84 → UTM Zone 33N). Validates output is within expected range and returns appropriate exit codes.

• sample_app/CMakeLists.txt - Build configuration using find_package(PROJ REQUIRED CONFIG) to link against installed library.

• build_sample.bat - Build script that configures, builds, tests, and packages the sample app using the install_proj output from the main build.

• .github/workflows/build_win.yml - Extended workflow to build sample app and upload as sample-app-windows artifact (executable + DLLs).

Example Usage

PJ *P = proj_create_crs_to_crs(ctx, "EPSG:4326", "EPSG:32633", NULL);
PJ *P_norm = proj_normalize_for_visualization(ctx, P);
PJ_COORD c_in = proj_coord(13.4050, 52.5200, 0, 0);  // Berlin
PJ_COORD c_out = proj_trans(P_norm, PJ_FWD, c_in);
// c_out.xy.x ≈ 391000, c_out.xy.y ≈ 5820000 (UTM Zone 33N)

The CI now produces two artifacts: the PROJ library installation and a working application that validates it.

• Fixes Build sample app with simple wgs to utm conversion to check installed library #1

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