Move ServerCard dimmed style to Card theme variant

Replaces inline style and opacity prop on ServerCard with a new
'disabled' variant on the Card theme, per AGENTS.md rules against
inline styles on components. Also picks up prettier formatting on
ResourcesScreen.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

clients/web/src/components/groups/ServerCard/ServerCard.tsx

@@ -113,8 +113,7 @@ export function ServerCard({
     <Card
       withBorder
       padding="lg"
-      opacity={isDimmed ? 0.4 : 1}
-      style={isDimmed ? { pointerEvents: "none" } : undefined}
+      variant={isDimmed ? "disabled" : undefined}
       {...(isDimmed ? { "aria-disabled": true, inert: true } : {})}
     >
       <Stack gap="sm">