fix: fall back to location.origin when VITE_KOMODO_HOST is empty string

[ahmd-soliman]

Closes #1359.

ui/Dockerfile defaults ARG VITE_KOMODO_HOST="", so any image built without overriding the ARG bakes the empty string into the bundle. ?? only falls back on null/undefined, so KOMODO_BASE_URL ends up as "". That breaks new WebSocket("/ws/update") (absolute URL required) and makes auth/API requests resolve against the page origin instead of the configured backend.

Switching to || covers the empty-string case while preserving the existing behavior for unset and real-URL values.

Reproduced locally with VITE_KOMODO_HOST="" yarn dev:

(await import('/src/main.tsx')).KOMODO_BASE_URL
// Before fix: ""
// After fix:  "http://localhost:5173"

Also verified with the env var unset — output is unchanged either way, so the dev path isn't affected.