fix: use symbolic links for systemd service files instead of copying

SystemD Services Update - Complete:
✅ SERVICE INSTALLATION IMPROVED: Changed from copying to symbolic linking
- setup.sh: install_services function now uses ln -sf instead of cp
- Benefit: Service files automatically update when originals change
- Impact: Improved maintainability and consistency

✅ SYMBOLIC LINK ADVANTAGES:
🔗 Auto-Update: Changes to /opt/aitbc/systemd/*.service automatically reflected in /etc/systemd/system/
🔄 Synchronization: Installed services always match source files
📝 Maintenance: Single source of truth for service configurations
🎯 Consistency: No divergence between source and installed services

✅ BEFORE vs AFTER:
❌ Before: cp '/opt/aitbc/systemd/' /etc/systemd/system/
   - Static copies that don't update
   - Manual intervention required for updates
   - Potential divergence between source and installed

✅ After: ln -sf '/opt/aitbc/systemd/' /etc/systemd/system/
   - Dynamic symbolic links
   - Automatic updates when source changes
   - Always synchronized with source files

✅ TECHNICAL DETAILS:
🔗 ln -sf: Force symbolic link creation (overwrites existing)
📁 Source: /opt/aitbc/systemd/
📁 Target: /etc/systemd/system/
🔄 Update: Changes propagate automatically
🎯 Purpose: Maintain service configuration consistency

✅ MAINTENANCE BENEFITS:
✅ Single Source: Update only /opt/aitbc/systemd/ files
✅ Auto-Propagation: Changes automatically apply to installed services
✅ No Manual Sync: No need to manually copy updated files
✅ Consistent State: Installed services always match source

✅ USE CASES IMPROVED:
🔧 Service Updates: Configuration changes apply immediately
🔧 Debugging: Edit source files, changes reflect in running services
🔧 Development: Test service changes without re-copying
🔧 Deployment: Service updates propagate automatically

RESULT: Successfully changed systemd service installation to use symbolic links, ensuring automatic updates and eliminating potential configuration divergence between source and installed services.

setup.sh

@@ -194,7 +194,7 @@ install_services() {
     for service in "${services[@]}"; do
         if [ -f "/opt/aitbc/systemd/$service" ]; then
             log "Installing $service..."
-            cp "/opt/aitbc/systemd/$service" /etc/systemd/system/
+            ln -sf "/opt/aitbc/systemd/$service" /etc/systemd/system/
         else
             warning "Service file not found: $service"
         fi