feat(deploy): single-image docker-compose and kubernetes install.sh

- multi-stage root Dockerfile (opsx-loki pattern): frontend dist +
  go binary + gh-ost in one alpine image, non-root user, HEALTHCHECK,
  entrypoint warning for missing SECRET_KEY; gin now serves the SPA
  from DIST_DIR (asset/db-logos/favicon passthrough, /api returns JSON
  404, SPA fallback to index.html) - one origin, no CORS surface
- docker-compose.yml rewritten: single service, named data volume,
  no-new-privileges + cap_drop ALL, /health healthcheck, resource
  limits, log rotation; SECRET_KEY required (openssl rand -hex 32),
  JWT_SECRET optional (auto-generated and persisted in prod)
- kubernetes/: install.sh one-command deploy (idempotent secret
  reuse, --nodeport/--ingress flags, rollout wait, backup tips) plus
  namespace/secret/pvc/deployment(single replica + Recreate, probes,
  resource limits, non-root)/service/nodeport/ingress manifests and
  README (sqlite single-writer constraints, snapshot backup)
- docs: README quick-start now has 3 deployment paths; ARCHITECTURE
  ch.14 expanded

single-image runtime verified locally (SPA/assets/api/login coexist
on :9002); full image build left to server (docker hub unreachable
from this machine)

kubernetes/secret.example.yaml

@@ -0,0 +1,13 @@
+# 密钥模板 —— 建议用 kubectl create secret 命令创建(install.sh 已自动处理),不要把真实值提交到仓库
+#   kubectl -n opsxsql create secret generic opsxsql-secrets \
+#     --from-literal=SECRET_KEY="$(openssl rand -hex 32)" \
+#     --from-literal=JWT_SECRET="$(openssl rand -hex 32)"
+apiVersion: v1
+kind: Secret
+metadata:
+  name: opsxsql-secrets
+  namespace: opsxsql
+type: Opaque
+stringData:
+  SECRET_KEY: "change-me-openssl-rand-hex-32"
+  JWT_SECRET: "change-me-openssl-rand-hex-32"