Remove dedicated superuser UI route and rename global admin

[demassimo]

Summary

• remove the dedicated /superuser nginx locations and rely on the main SPA entry point
• simplify the frontend to drop the special superuser UI mode while keeping admin navigation in-app
• relabel superuser affordances to Global admin and remove the unused standalone superuser UI bundle

Testing

• Not run (not requested)

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Codex Task

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve assets when hitting legacy /superuser/ path

Removing the dedicated /superuser locations means /superuser/… now falls through to the catch‑all location / (lines 36‑38), which serves index.html from that subpath. The SPA still references its JS/CSS with relative URLs like assets/app.js, so when the document is loaded at /superuser/ the browser requests /superuser/assets/..., which Nginx does not serve and instead returns HTML. Any operator following an existing /superuser/ bookmark now gets a broken page with no scripts or styles. Redirecting /superuser/* to / or making the asset URLs absolute is needed to keep the legacy entry point usable.

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