Feat v0.6.1-v0.6.2: backup/restore, docs surface, dynamic OpenAPI

v0.6.1 — Backup tooling (.swb ZIP export/import), admin backup section,
docs surface with markdown rendering, 5 reference docs, 6 handler tests.

v0.6.2 — Dark mode contrast fixes, topbar nav, 📖 docs icon, dynamic
OpenAPI spec with extension route merging, docs outline sidebar,
scroll/routing fixes; 7 new tests.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/js/sw/sdk/api-domains.js

@@ -277,6 +277,15 @@ export function createDomains(restClient) {
                 disable: (id)  => rc.put(`/api/v1/admin/surfaces/${id}/disable`, {}),
                 del:     (id)  => rc.del(`/api/v1/admin/surfaces/${id}`),
             },
+
+            // v0.6.1: Backup/Restore
+            backup: {
+                create:   (opts) => rc.post('/api/v1/admin/backup' + _qs(opts)),
+                list:     ()     => rc.get('/api/v1/admin/backups'),
+                download: (name) => `/api/v1/admin/backups/${name}`,
+                del:      (name) => rc.del(`/api/v1/admin/backups/${name}`),
+                restore:  (file) => rc.upload('/api/v1/admin/restore', file),
+            },
         },
 
         // ── Users ──────────────────────────────