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/index.tsx

@@ -2,6 +2,6 @@ import { createFileRoute, redirect } from '@tanstack/react-router'
 
 export const Route = createFileRoute('/_authenticated/')({
   beforeLoad: () => {
-    throw redirect({ to: '/accounts', search: {} as any })
+    throw redirect({ to: '/accounts', search: {} as Record<string, unknown> })
   },
 })