Add Temp Diagram and Fix Sidebar Nav

[TechHutTV]

Reverse Proxy docs: diagram, DNS note, and sidebar order

Changes

Reverse Proxy overview (src/pages/manage/reverse-proxy/index.mdx)

• Diagram: New “How it works” diagram showing:
  • HA cluster (e.g. *.eu.proxy.example.com) with multiple proxy nodes and WireGuard to a NetBird peer.
  • Non-HA cluster (e.g. *.us.proxy.example.com) with a single proxy.
  • Auth check and Management Service (netbird.example.com) in the flow.
• DNS note: Note for self-hosted deployments explaining that certificates require an A record for the NetBird host plus CNAME records for proxy and *.proxy, with a link to the self-hosted quickstart CNAME section.

Navigation (src/components/NavigationDocs.jsx)

• Sidebar: “Reverse Proxy” section moved so it appears after “Network Resources” (and its sub-pages) instead of before “Network Routes”.