ops: add CI/CD pipeline, a/b rolling deploy, Gitea Actions workflow

- .gitea/workflows/deploy.yml — push-to-main triggers rolling deploy
- scripts/deploy-bluegreen.sh — a-stack then b-stack restart; Maven runs
  in Docker (no JDK needed on runner host); Caddy reload at end
- scripts/deploy-all.ps1 — emergency manual deploy from dev machine
- infra/docker-compose.yml — a/b pairs per service; wget health checks;
  Gitea service; Prometheus/Grafana/DB ports restricted to localhost
- infra/Caddyfile — dual upstreams with health-based routing
- infra/Dockerfile.* — one per service
- infra/prometheus.yml + grafana provisioning

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/deploy.yml

@@ -0,0 +1,17 @@
+name: Deploy to Production
+
+on:
+  push:
+    branches: [main]
+
+jobs:
+  deploy:
+    runs-on: [self-hosted, host]
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 1
+
+      - name: Deploy (rolling zero-downtime)
+        run: bash scripts/deploy-bluegreen.sh