refactor(docker): optimize Dockerfiles for multi-stage builds and production deployment

- Implement multi-stage builds for main and speech Dockerfiles
- Reduce image size by using slim base images
- Improve dependency installation with frozen lockfile and production flags
- Add resource constraints and healthcheck to speech service Dockerfile
- Enhance build caching and separation of build/runtime dependencies

Dockerfile

@@ -1,14 +1,14 @@
 # Use Bun as the base image
-FROM oven/bun:1.0.25
+FROM oven/bun:1.0.25 as builder
 
 # Set working directory
 WORKDIR /app
 
-# Copy package files
-COPY package.json ./
+# Copy only package files first for better layer caching
+COPY package.json bun.lockb ./
 
-# Install dependencies
-RUN bun install
+# Install dependencies with production flag
+RUN bun install --frozen-lockfile --production
 
 # Copy source code
 COPY . .
@@ -16,6 +16,19 @@ COPY . .
 # Build TypeScript
 RUN bun run build
 
+# Create production image
+FROM oven/bun:1.0.25-slim
+
+WORKDIR /app
+
+# Copy only the necessary files from builder
+COPY --from=builder /app/dist ./dist
+COPY --from=builder /app/node_modules ./node_modules
+COPY package.json ./
+
+# Set production environment
+ENV NODE_ENV=production
+
 # Expose port
 EXPOSE 4000