fix: resolve all frontend lint errors and warnings

Replace all `any` types with proper types across 36 files:
- TanStack Router search params: `{} as Record<string, unknown>`
- API response pagination: proper typed interface
- DataTable column casts: remove unnecessary `as any`
- Function params and event handlers: use specific types
- Remove unused imports and variables in POS components

Frontend lint now passes with 0 errors and 0 warnings.

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

packages/admin/src/routes/_authenticated.tsx

@@ -67,7 +67,7 @@ function NavLink({ to, icon, label, collapsed }: { to: string; icon: React.React
   return (
     <Link
       to={to as '/accounts'}
-      search={{} as any}
+      search={{} as Record<string, unknown>}
       className="flex items-center gap-2 px-3 py-2 rounded-md text-sm text-sidebar-foreground hover:bg-sidebar-accent"
       activeProps={{ className: 'flex items-center gap-2 px-3 py-2 rounded-md text-sm bg-sidebar-accent text-sidebar-accent-foreground' }}
       title={collapsed ? label : undefined}