Remove @gfazioli/mantine-border-animate dependency, replace highlight with green border

[cliffhall]

Problem

The @gfazioli/mantine-border-animate dependency emits a persistent React warning in the Inspector console on every page load:

forwardRef render functions accept exactly two parameters: props and ref. Did you forget to use the ref parameter?

This warning originates inside the BorderAnimate component and clutters the console during development.

Where it's used

• clients/web/src/main.tsx — import "@gfazioli/mantine-border-animate/styles.css";
• clients/web/src/components/groups/ServerCard/ServerCard.tsx — wraps the server Card in <BorderAnimate show={highlighted} animate={highlighted} ...> to draw an animated border when a card is highlighted (e.g. scrolled-to / called out).
• clients/web/package.json / package-lock.json — declared dependency ^2.0.3.

Proposed fix

1. Remove the @gfazioli/mantine-border-animate dependency from clients/web/package.json (and re-lock).
2. Remove the styles.css import from main.tsx.
3. Replace the BorderAnimate highlight effect in ServerCard.tsx with a simple green border on the highlighted state instead of the animated border.
   • Drive it off the existing highlighted prop.
   • Use an --inspector-* CSS custom property for the green color (add a token to App.css :root if none fits) — no raw hex / rgba() literals.
   • Prefer a Mantine theme variant on Card (e.g. a highlighted variant in src/theme/Card.ts) over a CSS class, per project React/Mantine conventions.
4. Drop the w="100%" workaround comment/prop that only existed because BorderAnimate's wrapper was display:flex (verify card sizing still looks right without the wrapper).

Acceptance criteria

• No @gfazioli/mantine-border-animate references remain in the codebase.
• The forwardRef console warning is gone.
• Highlighting a server card shows a green border.
• Tests/coverage updated for the new highlight behavior; validate passes.