Expand CrowdSec IP reputation documentation

[TechHutTV]

Summary

Turns the selfhosted/maintenance/crowdsec page from a single-paragraph pointer into a full operational reference for the CrowdSec integration shipped in netbirdio/netbird#5722, netbirdio/netbird#5880, and netbirdio/dashboard#600.

• Introduces CrowdSec (local detection + crowdsourced feed) with a link to upstream docs
• New "How it works" section covers the LAPI container, stream bouncer lifecycle, per-service enforcement, the supports_crowdsec capability, and the NB_PROXY_CROWDSEC_API_* config surface
• "Enforcement modes" table plus a subsection clarifying that observe-mode verdicts are reviewed in the NetBird proxy event log (with the observe-mode badge), not in the CrowdSec Console
• "Enroll with the CrowdSec Console" steps for existing deployments
• "Testing the integration" section with bouncer-sync log check and a safe cscli decisions add self-test
• Adds a note that CrowdSec is currently self-hosted only, with Cloud support coming soon
• Adds two screenshots: crowdsec-overview.png and crowdsec-observe-badge.png