feat: add Docker development environment for frontend

Create containerized development setup for safe and consistent frontend development:

Docker Configuration:
- docker-compose.yml: Root-level orchestration with frontend service
- frontend/Dockerfile.dev: Node.js 20 Alpine optimized for dev
- Volume mounts for Hot Module Replacement (HMR)
- Named volume for node_modules to avoid conflicts
- Health check to verify service availability
- Environment variables for file watching (CHOKIDAR_USEPOLLING)

Vite Configuration Update:
- vite.config.ts: Add server config for Docker compatibility
- host: '0.0.0.0' to accept external connections
- usePolling: true for file watching in container
- port: 5173 explicitly configured

Documentation:
- README.md: Add Docker development procedure section
- Document docker compose up -d workflow
- Explain HMR and hot-reload capabilities
- List advantages of Docker-based development

Usage:
  docker compose up -d        # Start development server
  docker compose logs -f      # View logs
  docker compose down         # Stop container

Access: http://localhost:5173

Safety First:
- Isolated environment prevents system conflicts
- Reproducible setup across different machines
- No host Node.js installation required
- Easy team onboarding

Refs: Docker best practices for Node.js development

frontend/Dockerfile.dev

@@ -0,0 +1,26 @@
+# Dockerfile.dev - Development container for LogWhisperer AI Frontend
+# Optimized for Node.js with Hot Module Replacement (HMR)
+
+FROM node:20-alpine
+
+# Set working directory
+WORKDIR /app
+
+# Install dependencies for file watching (needed for HMR in Docker)
+RUN apk add --no-cache git
+
+# Copy package files first (for better caching)
+COPY package*.json ./
+
+# Install dependencies
+RUN npm ci
+
+# Copy the rest of the application
+COPY . .
+
+# Expose port 5173 for Vite dev server
+EXPOSE 5173
+
+# Command to run the development server
+# Using --host 0.0.0.0 to allow connections from outside the container
+CMD ["npm", "run", "dev", "--", "--host", "0.0.0.0"]

frontend/vite.config.ts

@@ -4,4 +4,11 @@ import react from '@vitejs/plugin-react'
 // https://vite.dev/config/
 export default defineConfig({
   plugins: [react()],
+  server: {
+    host: '0.0.0.0',
+    port: 5173,
+    watch: {
+      usePolling: true,
+    },
+  },
 })