feat(k8s): 新增 core 真应用(前端+Django API+Celery worker)构建与部署

- core/frontend: Vite 多阶段镜像 + nginx 同源反代 /api,/admin,/static(零 CORS)
- core/backend: Django gunicorn 镜像 + entrypoint(自动 migrate/collectstatic)+ WhiteNoise
- k8s/core: api/worker/web Deployment+Service + ingress(airshelf-web.airlabs.art)
- workflow: 追加 core 前后端 build/push,从 core/backend/.env 套生产覆盖生成 env Secret 后部署
- .gitignore 放行 core/backend/.env;.env 白名单加入 airshelf-web 域名
- 含前端 WIP 还原改动

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

k8s/core/api-deployment.yaml

@@ -0,0 +1,70 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: airshelf-core-api
+  labels:
+    app: airshelf-core-api
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: airshelf-core-api
+  template:
+    metadata:
+      labels:
+        app: airshelf-core-api
+    spec:
+      imagePullSecrets:
+      - name: cr-pull-secret
+      containers:
+      - name: airshelf-core-api
+        image: ${CI_REGISTRY_IMAGE}/airshelf-core-api:latest
+        imagePullPolicy: Always
+        # No command override: the image ENTRYPOINT (docker-entrypoint.sh) runs
+        # migrate + collectstatic, then the default CMD (gunicorn) is exec'd.
+        ports:
+        - containerPort: 8000
+        envFrom:
+        - secretRef:
+            name: airshelf-core-env
+        livenessProbe:
+          httpGet:
+            path: /api/health/
+            port: 8000
+            httpHeaders:
+            - name: Host
+              value: airshelf-web.airlabs.art
+          initialDelaySeconds: 20
+          periodSeconds: 15
+          timeoutSeconds: 5
+          failureThreshold: 3
+        readinessProbe:
+          httpGet:
+            path: /api/health/
+            port: 8000
+            httpHeaders:
+            - name: Host
+              value: airshelf-web.airlabs.art
+          initialDelaySeconds: 10
+          periodSeconds: 10
+          timeoutSeconds: 5
+          failureThreshold: 3
+        resources:
+          requests:
+            memory: "256Mi"
+            cpu: "100m"
+          limits:
+            memory: "768Mi"
+            cpu: "1000m"
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: airshelf-core-api
+spec:
+  selector:
+    app: airshelf-core-api
+  ports:
+    - protocol: TCP
+      port: 8000
+      targetPort: 8000