fix(ui): login screen shows the product name

[pyramation]

Summary

The login screen's heading was still the old project name, so operators saw a different name there than everywhere else in the app (page title, desktop shell). Now it reads WAVEGRID, matching packages/ui/index.html. Tagline and styling unchanged.

Link to Devin session: https://app.devin.ai/sessions/ec43152136134467a853ec0bbf783ea9
Requested by: @pyramation

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