ci: add GitHub Actions workflows for multi-platform builds

- Add build-linux.yml for Ubuntu/Linux x86_64 builds
  - Installs required system dependencies (webkit2gtk, GTK3, etc.)
  - Builds Tauri application for Linux platform
  - Uploads build artifacts for distribution

- Add build-macos.yml for macOS Intel and Apple Silicon builds
  - Supports both x86_64 and aarch64 architectures
  - Handles Apple certificate import and code signing
  - Creates notarized DMG installers
  - Includes Homebrew cask generation
  - Allows skipping builds and using previous artifacts

- Add release.yml for automated releases
  - Triggers on version tags (v*)
  - Orchestrates builds across all platforms
  - Creates GitHub releases with all artifacts
  - Supports manual workflow dispatch with version input

.github/workflows/build-linux.yml

@@ -0,0 +1,60 @@
+name: Build Linux
+
+on:
+  workflow_dispatch:
+  push:
+    branches: [main, test-linux-workflow]
+
+jobs:
+  build:
+    name: Build Linux x86_64
+    runs-on: ubuntu-latest
+    
+    steps:
+      - uses: actions/checkout@v4
+      
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y \
+            pkg-config \
+            libwebkit2gtk-4.1-dev \
+            libgtk-3-dev \
+            libssl-dev \
+            libayatana-appindicator3-dev \
+            librsvg2-dev
+      
+      - name: Setup Rust
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: x86_64-unknown-linux-gnu
+      
+      - name: Setup Rust cache
+        uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: src-tauri
+      
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+      
+      - name: Install dependencies
+        run: bun install
+      
+      - name: Build Tauri app
+        run: bun run tauri build --target x86_64-unknown-linux-gnu
+      
+      - name: Create artifacts directory
+        run: |
+          mkdir -p dist/linux-x86_64
+          cp src-tauri/target/x86_64-unknown-linux-gnu/release/bundle/deb/*.deb dist/linux-x86_64/ || true
+          cp src-tauri/target/x86_64-unknown-linux-gnu/release/bundle/appimage/*.AppImage dist/linux-x86_64/ || true
+          
+          # Generate checksums
+          cd dist/linux-x86_64
+          sha256sum * > checksums.txt
+      
+      - name: Upload artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: linux-x86_64
+          path: dist/linux-x86_64/*