Create a build workflow

.github/workflows/build.yml

@@ -0,0 +1,47 @@
+name: Build Electron Apps
+
+on:
+  workflow_dispatch:
+  push:
+    branches: ["main", "electron"]
+    paths:
+      - 'frontend/**'
+      - 'package.json'
+      - 'package-lock.json'
+      - 'frontend/electron/**'
+
+jobs:
+  build:
+    name: Build (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '24'
+
+      - name: Install root deps (no scripts)
+        run: npm install --ignore-scripts --no-audit --no-fund
+
+      - name: Install Electron Forge deps
+        run: npm run frontend:electron:dependencies
+
+      - name: Build Electron app
+        run: npm run build:electron
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: fromchat-${{ runner.os }}
+          path: |
+            frontend/electron/forge/out/**
+          if-no-files-found: error
+