feat: initial health-app with Express API and GitOps CI/CD

Node.js Express app with /health, /ready, / endpoints.
Multi-stage Dockerfile, GitHub Actions pipeline for GHCR push
and gitops-infra manifest auto-update.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,27 @@
+# Stage 1: Install dependencies
+FROM node:20-alpine AS deps
+WORKDIR /app
+COPY package.json package-lock.json* ./
+RUN npm ci --omit=dev && npm cache clean --force
+
+# Stage 2: Production image
+FROM node:20-alpine AS runtime
+ENV NODE_ENV=production
+WORKDIR /app
+
+RUN addgroup -g 1001 -S appgroup && \
+    adduser -u 1001 -S appuser -G appgroup
+
+COPY --from=deps /app/node_modules ./node_modules
+COPY src ./src
+COPY package.json ./
+
+RUN chown -R appuser:appgroup /app
+USER appuser
+
+EXPOSE 3000
+
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
+  CMD wget -qO- http://localhost:3000/health || exit 1
+
+CMD ["node", "src/server.js"]