ci: build the Windows client on GitHub and Gitea

GitHub builds natively on windows-latest; Gitea cross-compiles with MinGW
on a Linux runner. Both upload the client with its assets and publish a
zip for v* tags.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.gitea/workflows/windows-client.yml

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+# Gitea Actions: cross-compiles the Windows client on a Linux runner with MinGW,
+# since most Gitea runners are Linux containers.
+name: Windows client
+
+on:
+  push:
+    branches: [main]
+    tags: ["v*"]
+  pull_request:
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+  CARGO_INCREMENTAL: 0
+  TARGET: x86_64-pc-windows-gnu
+
+jobs:
+  build:
+    name: Build Windows client
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install MinGW
+        run: |
+          SUDO=$(command -v sudo || true)
+          $SUDO apt-get update
+          $SUDO apt-get install -y --no-install-recommends gcc-mingw-w64-x86-64 zip
+
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: ${{ env.TARGET }}
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: windows-gnu-${{ hashFiles('Cargo.lock') }}
+          restore-keys: windows-gnu-
+
+      - name: Build
+        run: cargo build --release --locked -p game_client --bin game --target "$TARGET"
+
+      - name: Package
+        run: |
+          dist=dist/station-windows
+          mkdir -p "$dist"
+          cp "target/$TARGET/release/game.exe" "$dist/"
+          cp -r assets README.md "$dist/"
+          (cd dist && zip -qr station-windows.zip station-windows)
+
+      # Gitea does not support upload-artifact v4.
+      - name: Upload artifact
+        uses: actions/upload-artifact@v3
+        with:
+          name: station-windows
+          path: dist/station-windows
+          if-no-files-found: error
+
+      - name: Publish release
+        if: startsWith(github.ref, 'refs/tags/v')
+        uses: https://gitea.com/actions/release-action@main
+        with:
+          files: dist/station-windows.zip
+          api_key: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/windows-client.yml

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+name: Windows client
+
+on:
+  push:
+    branches: [main]
+    tags: ["v*"]
+  pull_request:
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  CARGO_TERM_COLOR: always
+  CARGO_INCREMENTAL: 0
+
+jobs:
+  build:
+    name: Build Windows client
+    runs-on: windows-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Cache cargo
+        uses: Swatinem/rust-cache@v2
+
+      - name: Build
+        run: cargo build --release --locked -p game_client --bin game
+
+      - name: Package
+        shell: pwsh
+        run: |
+          $dist = "dist/station-windows"
+          New-Item -ItemType Directory -Force -Path $dist | Out-Null
+          Copy-Item target/release/game.exe $dist/
+          Copy-Item -Recurse assets $dist/assets
+          Copy-Item README.md $dist/
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: station-windows
+          path: dist/station-windows
+          if-no-files-found: error
+
+      - name: Create release archive
+        if: startsWith(github.ref, 'refs/tags/v')
+        shell: pwsh
+        run: Compress-Archive -Path dist/station-windows/* -DestinationPath dist/station-windows.zip
+
+      - name: Publish release
+        if: startsWith(github.ref, 'refs/tags/v')
+        uses: softprops/action-gh-release@v2
+        with:
+          files: dist/station-windows.zip