ci: add workflow to build and release binaries

Added GitHub Actions workflow to automatically build binaries
when releases are published by release-plz.

Platforms supported (10 total):
- Linux: x86_64/aarch64 (gnu and musl variants)
- macOS: x86_64/aarch64 (Intel and Apple Silicon)
- Windows: x86_64/aarch64

Features:
- Triggers on GitHub release published event
- Manual trigger with tag input for existing releases
- Cross-compilation using taiki-e/upload-rust-binary-action
- Workspace-aware with manifest-path to crates/ccsync
- Archives: .tar.gz for Unix, .zip for Windows
- Uploads binaries directly to GitHub release

Usage:
- Automatic: Push to master → release-plz creates release → binaries built
- Manual: Actions → Release Binaries → Run workflow → Enter tag

This enables users to download pre-built binaries instead of
building from source.

Author: onsails

.github/workflows/release-binaries.yml

@@ -0,0 +1,65 @@
+name: Release Binaries
+
+on:
+  release:
+    types: [published]
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Tag to build binaries for (e.g., v0.1.3)'
+        required: true
+        type: string
+
+permissions:
+  contents: write
+
+jobs:
+  upload-binaries:
+    name: Build and upload binaries
+    # Build binaries for all releases (workspace uses single version)
+    if: github.repository_owner == 'onsails'
+    strategy:
+      matrix:
+        include:
+          # Linux
+          - target: x86_64-unknown-linux-gnu
+            os: ubuntu-latest
+          - target: aarch64-unknown-linux-gnu
+            os: ubuntu-latest
+          - target: x86_64-unknown-linux-musl
+            os: ubuntu-latest
+          - target: aarch64-unknown-linux-musl
+            os: ubuntu-latest
+
+          # macOS
+          - target: x86_64-apple-darwin
+            os: macos-latest
+          - target: aarch64-apple-darwin
+            os: macos-latest
+
+          # Windows
+          - target: x86_64-pc-windows-msvc
+            os: windows-latest
+          - target: aarch64-pc-windows-msvc
+            os: windows-latest
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.inputs.tag || github.ref }}
+
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Upload binary to release
+        uses: taiki-e/upload-rust-binary-action@v1
+        with:
+          bin: ccsync
+          manifest-path: crates/ccsync/Cargo.toml
+          target: ${{ matrix.target }}
+          tar: all
+          zip: windows
+          token: ${{ secrets.GITHUB_TOKEN }}