crypto.randomUUID is restricted to secure contexts (HTTPS or localhost).
When RefBoard is served over plain HTTP on a LAN IP (e.g.
http://192.168.x.x:8000), the function is undefined and the editor crashes
on first ID generation with:
Uncaught TypeError: crypto.randomUUID is not a function
The frontend calls crypto.randomUUID in ~20 places (uploadManager,
SceneManager, Editor, canvas tools, grouping, scene-format, etc.), so a
single polyfill at the entry point is the smallest fix.
The polyfill uses crypto.getRandomValues — available on insecure origins —
to build an RFC 4122 v4 UUID with the correct version/variant bits. It is
a no-op when the native function exists, so HTTPS and localhost paths are
unchanged.
No crypto.subtle usage exists in the source, so randomUUID is the only
secure-context API the frontend depends on today.
