add cross-platform CI build workflow

.github/workflows/build.yml

@@ -0,0 +1,84 @@
+name: build
+
+on:
+  push:
+    tags:
+      - 'v*'
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Release tag to upload assets to'
+        required: true
+        default: 'v1.0.0'
+
+jobs:
+  create-release:
+    runs-on: ubuntu-latest
+    outputs:
+      tag: ${{ steps.tag.outputs.value }}
+    steps:
+      - name: Resolve tag
+        id: tag
+        run: |
+          if [ "${{ github.event_name }}" = "workflow_dispatch" ]; then
+            echo "value=${{ inputs.tag }}" >> $GITHUB_OUTPUT
+          else
+            echo "value=${{ github.ref_name }}" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Ensure release exists
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          gh release view "${{ steps.tag.outputs.value }}" --repo "${{ github.repository }}" 2>/dev/null || \
+          gh release create "${{ steps.tag.outputs.value }}" \
+            --repo "${{ github.repository }}" \
+            --title "${{ steps.tag.outputs.value }}" \
+            --generate-notes
+
+  build:
+    needs: create-release
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: windows-latest
+            artifact: WarehouseMaster.exe
+          - os: macos-latest
+            artifact: WarehouseMaster-macos
+          - os: ubuntu-latest
+            artifact: WarehouseMaster-linux
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Install system deps (Linux)
+        if: runner.os == 'Linux'
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y libxcb-xinerama0 libgl1 libegl1
+
+      - name: Install Python deps
+        run: pip install pyinstaller -r requirements.txt
+
+      - name: Build
+        env:
+          QT_QPA_PLATFORM: offscreen
+        run: pyinstaller WarehouseMaster.spec
+
+      - name: Rename artifact (macOS/Linux)
+        if: runner.os != 'Windows'
+        shell: bash
+        run: mv dist/WarehouseMaster "dist/${{ matrix.artifact }}"
+
+      - name: Upload to release
+        shell: bash
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: gh release upload "${{ needs.create-release.outputs.tag }}" "dist/${{ matrix.artifact }}" --clobber