add the officer-headscale sidecar and its server registry ui

officer-headscale owns the whole Headscale contract: the registered servers and
their admin api keys, the >=0.29 version floor, and every multi-call composition
the ui needs. the platform side is auth+forward only and holds no headscale
credentials, so the existing /api/vpn/enroll route and its HEADSCALE_* env vars
are untouched and unrelated.

officer manages many servers rather than one. the owner registers each with a url
and a key generated on that server and switches between them; exactly one is
active, enforced by a partial unique index rather than by convention. keys are
encrypted at rest and never leave the sidecar — the list projection cannot return
one. registration validates before it saves: an unauthenticated GET /version to
prove something headscale-shaped is there and meets the floor, then an
authenticated call to prove the key works. an edit that moves either half
re-validates.

there is deliberately no transparent /api/v1/* passthrough. headscale serialises
every uint64 as a json string and its rest shape moved repeatedly below 0.29;
proxying raw would push all of that into the browser, which is the mistake the
soulseek panels made with 37 raw upstream calls.

the /headscale workspace is nav + view over the panel system. only the servers
section is implemented — nodes, users and pre-auth keys say so plainly rather
than rendering an empty table that reads as a failed fetch.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/apps/officer-web/Screens/Dashboard/Headscale/defaultLayout.ts

@@ -0,0 +1,11 @@
+import type { LayoutNode } from 'officerdev';
+
+export const defaultLayout: LayoutNode = {
+  type: 'group',
+  id: 'headscale-root',
+  direction: 'horizontal',
+  children: [
+    { node: { type: 'panel', id: 'headscale-nav', appType: 'headscale-nav' }, size: 22 },
+    { node: { type: 'panel', id: 'headscale-view', appType: 'headscale-view' }, size: 78 },
+  ],
+};