Fix Docker networking and add graceful MongoDB error handling

- Fix DNS resolution: Removed invalid dns_search configuration
- Add graceful MongoDB connection error handling
- Set restart policy to 'unless-stopped' for both services
- Add development helper scripts (start-dev.sh, stop-dev.sh)
- Update Docker Compose configurations for development
- Restore main.rs from git history
- Backend now logs MongoDB errors without crashing

All containers now start successfully with proper DNS resolution
on the dedicated normogen-network.

backend/stop-dev.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+set -e
+
+echo "🛑 Stopping Normogen Backend Development Environment..."
+cd "$(dirname "$0")"
+
+docker-compose -f docker-compose.dev.yml down
+
+echo "✅ Development environment stopped!"