feat(docker): add frontend service to docker-compose with env config improvements (#10536)

## Summary
This PR adds the frontend service to the Docker Compose configuration,
enabling `docker compose up` to run the complete stack including the
frontend. It also implements comprehensive environment variable
improvements and fixes Docker networking issues.

## Key Changes

### 🐳 Docker Compose Improvements
- **Added frontend service** to `docker-compose.yml` and
`docker-compose.platform.yml`
- **Production build**: Uses `pnpm build + serve` instead of dev server
for better stability and lower memory usage
- **Service dependencies**: Frontend now waits for backend services
(`rest_server`, `websocket_server`) to be ready
- **YAML anchors**: Implemented DRY configuration to avoid duplicating
environment values

### 🔧 Environment Variable Architecture
- **Dual environment strategy**: 
- Server-side code uses Docker service names
(`http://rest_server:8006/api`)
  - Client-side code uses localhost URLs (`http://localhost:8006/api`)
- **Comprehensive config**: Added build args and runtime environment
variables
- **Network compatibility**: Fixes connection issues between frontend
and backend containers

### 🛠️ Code Improvements
- **Centralized env-config helper** (`/frontend/src/lib/env-config.ts`)
with server-side priority
- **Updated all frontend code** to use shared environment helpers
instead of direct `process.env` access
- **Consistent API**: All environment variable access now goes through
helper functions

### 🔗 Files Changed
- `docker-compose.yml` & `docker-compose.platform.yml` - Added frontend
service
- `frontend/Dockerfile` - Added build args for environment variables
- `frontend/src/lib/env-config.ts` - New centralized environment
configuration
- Multiple frontend files - Updated to use env helpers

## Benefits
- ✅ **Single command deployment**: `docker compose up` now runs
everything
- ✅ **Better reliability**: Production build reduces memory usage and
crashes
- ✅ **Network compatibility**: Proper container-to-container
communication
- ✅ **Maintainable config**: Centralized environment variable management
- ✅ **Development friendly**: Works in both Docker and local development

## Testing
- ✅ Verified Docker service communication works correctly
- ✅ Frontend responds and serves content properly  
- ✅ Environment variables are correctly resolved in both server and
client contexts
- ✅ No connection errors after implementing service dependencies

🤖 Generated with [Claude Code](https://claude.ai/code)

---------

Co-authored-by: Claude <noreply@anthropic.com>

.github/workflows/platform-frontend-ci.yml

@@ -195,7 +195,7 @@ jobs:
 
       - name: Run docker compose
         run: |
-          docker compose -f ../docker-compose.yml up -d
+          NEXT_PUBLIC_PW_TEST=true docker compose -f ../docker-compose.yml up -d
         env:
           DOCKER_BUILDKIT: 1
           BUILDX_CACHE_FROM: type=local,src=/tmp/.buildx-cache
@@ -258,8 +258,6 @@ jobs:
       - name: Build frontend
         run: pnpm build --turbo
         # uses Turbopack, much faster and safe enough for a test pipeline
-        env:
-          NEXT_PUBLIC_PW_TEST: true
 
       - name: Install Browser 'chromium'
         run: pnpm playwright install --with-deps chromium