Add OpenAPI specification generation workflow

This workflow generates an OpenAPI specification and uploads it as an artifact.

.github/workflows/openapi.yml

@@ -0,0 +1,32 @@
+name: Generate OpenAPI Specification
+
+on:
+  workflow_dispatch:
+
+jobs:
+  generate-openapi:
+    name: Generate OpenAPI JSON
+    runs-on: blacksmith-2vcpu-ubuntu-2404
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: "20"
+          cache: "npm"
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Generate OpenAPI specification
+        run: npm run generate:openapi
+
+      - name: Upload OpenAPI artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: openapi-spec
+          path: openapi.json
+          retention-days: 90