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>

core/backend/airshelf/settings/production.py

@@ -1,4 +1,7 @@
+from pathlib import Path
+
 from .base import *  # noqa: F403
+from .base import BASE_DIR, MIDDLEWARE
 
 
 DEBUG = False
@@ -6,3 +9,16 @@ SECURE_PROXY_SSL_HEADER = ("HTTP_X_FORWARDED_PROTO", "https")
 SESSION_COOKIE_SECURE = True
 CSRF_COOKIE_SECURE = True
 
+# Serve admin/static behind gunicorn with DEBUG=False (no nginx static mount needed).
+# WhiteNoise sits right after SecurityMiddleware.
+MIDDLEWARE = (
+    MIDDLEWARE[:1]
+    + ["whitenoise.middleware.WhiteNoiseMiddleware"]
+    + MIDDLEWARE[1:]
+)
+
+STATIC_ROOT = Path(BASE_DIR) / "staticfiles"
+STORAGES = {
+    "default": {"BACKEND": "django.core.files.storage.FileSystemStorage"},
+    "staticfiles": {"BACKEND": "whitenoise.storage.CompressedManifestStaticFilesStorage"},
+}