docs: add log management page

[narcisonunez]

Adds a Core docs page for Log Management, the feature from Dokploy/dokploy#5408 that ships container logs to external providers with a Vector agent.

The page covers:

• the supported providers and their fields
• adding a provider and testing the connection
• deploying the agent per server
• applying changes with Redeploy
• the dokploy.* log metadata
• the multi-organization behavior on the Dokploy server
• Dokploy Cloud limits and troubleshooting

It's listed in core/meta.json under Server, after Backups.

Merge this together with Dokploy/dokploy#5408.