Update Dockerfile to multi-stage build that compiles TypeScript

Dockerfile

@@ -1,12 +1,25 @@
+# ---- Build stage ----------------------------------------------------------
+FROM node:20-alpine AS builder
+
+WORKDIR /app
+
+COPY package*.json tsconfig.json ./
+RUN npm install --no-audit --no-fund
+
+COPY src/ ./src/
+RUN npm run build
+
+# ---- Runtime stage --------------------------------------------------------
 FROM node:20-alpine
 
 WORKDIR /app
 
-# Install production dependencies
+# Install only production dependencies
 COPY package*.json ./
-RUN npm install --omit=dev && npm cache clean --force
+RUN npm install --omit=dev --no-audit --no-fund && npm cache clean --force
 
-# Copy application code
+# Copy compiled output and entry point
+COPY --from=builder /app/dist ./dist
 COPY server.js ./
 
 # Run as non-root user for security