fix: replace all remaining old brand tokens (text-brand-dark, border-brand-border, bg-white opacity)

30 references to removed CSS variables: border-brand-border → border-[#1e2130],
text-brand-text-muted → text-[#4f5666], text-brand-dark → text-white,
bg-white/[0.04] → bg-[#191c25], hover:border-white/[0.12] → hover:border-[#2a2f3d].

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

frontend/src/components/session/TicketPickerModal.tsx

@@ -290,7 +290,7 @@ export function TicketPickerModal({ open, onClose, sessionId, onLinked, onSelect
                     disabled={isLooking}
                     className={cn(
                       'w-full rounded-lg border border-transparent px-3 py-2.5 text-left transition-all',
-                      'hover:border-[#1e2130] hover:bg-white/[0.04]',
+                      'hover:border-[#1e2130] hover:bg-[#191c25]',
                       'disabled:opacity-50',
                       result.closed && 'opacity-60'
                     )}