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/state/usePageTitle.ts

@@ -17,6 +17,7 @@ const RULES: TitleRule[] = [
   { match: (p) => p.startsWith('/files'), title: 'Files' },
   { match: (p) => p.startsWith('/music'), title: 'Music' },
   { match: (p) => p.startsWith('/soulseek'), title: 'Soulseek' },
+  { match: (p) => p.startsWith('/headscale'), title: 'Headscale' },
   { match: (p) => p.startsWith('/system-monitor'), title: 'System Monitor' },
   { match: (p) => p.startsWith('/code-editor'), title: 'Code Editor' },
   { match: (p) => p.startsWith('/task-logs'), title: 'Task Logs' },