feat(release): add GoReleaser config and Homebrew tap support

Enable `brew install multica-cli` via multica-ai/homebrew-tap.
GoReleaser builds cross-platform binaries (macOS/Linux, amd64/arm64)
and auto-updates the Homebrew formula on tagged releases.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/release.yml

@@ -0,0 +1,33 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - "v*"
+
+permissions:
+  contents: write
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: "1.24"
+          cache-dependency-path: server/go.sum
+
+      - name: Run GoReleaser
+        uses: goreleaser/goreleaser-action@v6
+        with:
+          version: "~> v2"
+          args: release --clean
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          HOMEBREW_TAP_GITHUB_TOKEN: ${{ secrets.HOMEBREW_TAP_GITHUB_TOKEN }}