Deletes /wg-server (route, handlers, template) entirely and adds generic
/servers/:id/interface and /servers/:id/keypair endpoints + UI in the
All Servers page, so every server (including the default one) is managed
through the same per-server registry. Drops the write-through dual-write
hacks that kept the old single-server collection in sync - the registry
is now the single source of truth. One-time legacy-install migration path
is untouched.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
