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/login.tsx

@@ -7,7 +7,7 @@ export const Route = createFileRoute('/login')({
   beforeLoad: () => {
     const { token } = useAuthStore.getState()
     if (token) {
-      throw redirect({ to: '/accounts', search: {} as any })
+      throw redirect({ to: '/accounts', search: {} as Record<string, unknown> })
     }
   },
   component: LoginPage,
@@ -30,7 +30,7 @@ function LoginPage() {
       const res = await login(email, password)
       setAuth(res.token, res.user)
       await router.invalidate()
-      await router.navigate({ to: '/accounts', search: {} as any, replace: true })
+      await router.navigate({ to: '/accounts', search: {} as Record<string, unknown>, replace: true })
     } catch (err) {
       setError(err instanceof Error ? err.message : 'Login failed')
     } finally {