feat(cli): add bundled health app scaffold and init command

- ship OpenAPI-first health check template as package data
- add CLI to copy scaffold into new project directories
- include OpenAPI spec, routes, and bootstrap example
- enable fast startup for OpenAPI-first services

openapi_first/templates/health_app/openapi.yaml

@@ -0,0 +1,22 @@
+openapi: 3.0.3
+info:
+  title: Health Check Service
+  version: "1.0.0"
+
+paths:
+  /health:
+    get:
+      operationId: get_health
+      summary: Service health check
+      description: Returns basic liveness status of the service.
+      responses:
+        "200":
+          description: Service is healthy
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  status:
+                    type: string
+                    example: ok