ci(forgejo): add Actions for test, build, and releases

Host-mode workflows run Go inside golang:1.25-bookworm. CI covers
push/PR; tagged v* builds multi-arch artifacts and publishes a Forgejo
release.

.forgejo/workflows/ci.yml

@@ -0,0 +1,40 @@
+# Host-mode runner: no local Go — use official golang image + docker.sock.
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+concurrency:
+  group: magpie-ci-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    name: Test and build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: https://data.forgejo.org/actions/checkout@v4
+
+      - name: Go test and build
+        run: |
+          set -euo pipefail
+          case "$GITHUB_WORKSPACE" in
+            /data/*) HOST_WORKSPACE="/opt/forgejo-runner/data${GITHUB_WORKSPACE#/data}" ;;
+            *) HOST_WORKSPACE="$GITHUB_WORKSPACE" ;;
+          esac
+          test -f "$GITHUB_WORKSPACE/go.mod"
+          docker run --rm --network host \
+            --volume "$HOST_WORKSPACE:/src" \
+            --workdir /src \
+            -e CGO_ENABLED=0 \
+            golang:1.25-bookworm \
+            bash -lc '
+              set -euo pipefail
+              go version
+              go test ./...
+              make build
+              ls -la dist/
+            '