fix(magic): explicit imports + staging defaults + sheet height
- backend/api/magic/register: explicit import of MAGIC_DEVICE_LIMIT
and createAdGuardClient (Nitro auto-import was missing them
→ ReferenceError → HTTP 500 on /api/magic/register)
- mac-app: default backendBaseUrl falls back to staging.rebreak.org
(app.rebreak.org serves wrong TLS cert)
- native MagicSheet: fallback download/dmg URLs point to staging
- native settings: Magic sheet capped at detents=[0.85] so AppHeader
stays visible
- bundles all in-flight Magic feature work (pair create/redeem,
device endpoints, schema, adguard utils, mac-app, locales)
77edd67cbe