Implement FarmQ Admin machine name display fix for Magic DNS

Fix machine management page to display proper Magic DNS names:
- Use given_name instead of hostname for machine display
- Add Magic DNS address with copy-to-clipboard functionality
- Distinguish between machine name and OS hostname like Headplane
- Enhance UI with Magic DNS information (.headscale.local)

Changes:
- farmq-admin/utils/database_new.py: Use given_name for machine_name
- farmq-admin/models/farmq_models.py: Update sync logic for given_name
- farmq-admin/templates/machines/list.html: Add Magic DNS display with copy feature
- FARMQ_ADMIN_MACHINE_NAME_FIX_PLAN.md: Complete analysis and implementation plan

Now displays:
- Machine Name: pbs-hp (Magic DNS name)
- Magic DNS: pbs-hp.headscale.local (with copy button)
- OS Hostname: proxmox-backup-server (system name)

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

Co-Authored-By: Claude <noreply@anthropic.com>

farmq-admin/models/farmq_models.py

@@ -432,6 +432,7 @@ class FarmqDatabaseManager:
             if machine:
                 # 기존 머신 업데이트
                 machine.hostname = headscale_node_data.get('hostname')
+                machine.machine_name = headscale_node_data.get('given_name') or headscale_node_data.get('hostname')
                 machine.tailscale_ip = headscale_node_data.get('ipv4')
                 machine.tailscale_status = 'online' if headscale_node_data.get('is_online') else 'offline'
                 machine.last_seen = datetime.now()
@@ -442,7 +443,7 @@ class FarmqDatabaseManager:
                     headscale_node_id=headscale_node_data.get('id'),
                     headscale_machine_key=headscale_node_data.get('machine_key'),
                     hostname=headscale_node_data.get('hostname'),
-                    machine_name=headscale_node_data.get('hostname'),
+                    machine_name=headscale_node_data.get('given_name') or headscale_node_data.get('hostname'),
                     tailscale_ip=headscale_node_data.get('ipv4'),
                     tailscale_status='online' if headscale_node_data.get('is_online') else 'offline',
                     last_seen=datetime.now()