ci: build Windows binaries; add cross-platform CI test matrix

- release.yml: add x86_64-pc-windows-msvc target, OS-aware packaging (.exe + .zip)
- ci.yml: split into lint (fmt/clippy) + test matrix (ubuntu/windows/macos)
- use getrandom for the admin/key token CSPRNG (secure on Windows too)

.github/workflows/release.yml

@@ -36,6 +36,8 @@ jobs:
             target: x86_64-unknown-linux-gnu
           - os: macos-14
             target: aarch64-apple-darwin
+          - os: windows-latest
+            target: x86_64-pc-windows-msvc
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
@@ -47,12 +49,19 @@ jobs:
       - name: Package
         shell: bash
         run: |
+          bin=cortiq-gateway
+          [ "${{ runner.os }}" = "Windows" ] && bin=cortiq-gateway.exe
           staging="cortiq-gateway-${{ github.ref_name }}-${{ matrix.target }}"
           mkdir "$staging"
-          cp "target/${{ matrix.target }}/release/cortiq-gateway" "$staging"/
+          cp "target/${{ matrix.target }}/release/$bin" "$staging"/
           cp README.md LICENSE config/gateway.example.toml "$staging"/
-          tar czf "$staging.tar.gz" "$staging"
-          echo "ASSET=$staging.tar.gz" >> "$GITHUB_ENV"
+          if [ "${{ runner.os }}" = "Windows" ]; then
+            7z a "$staging.zip" "$staging" >/dev/null
+            echo "ASSET=$staging.zip" >> "$GITHUB_ENV"
+          else
+            tar czf "$staging.tar.gz" "$staging"
+            echo "ASSET=$staging.tar.gz" >> "$GITHUB_ENV"
+          fi
       - name: Release
         uses: softprops/action-gh-release@v2
         with: