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/components/pos/pos-item-panel.tsx

@@ -14,7 +14,7 @@ interface POSItemPanelProps {
   transaction: Transaction | null
 }
 
-export function POSItemPanel({ transaction }: POSItemPanelProps) {
+export function POSItemPanel({ transaction: _transaction }: POSItemPanelProps) {
   const queryClient = useQueryClient()
   const { currentTransactionId, setTransaction, locationId } = usePOSStore()
   const [search, setSearch] = useState('')

packages/admin/src/components/pos/pos-register.tsx

@@ -1,5 +1,5 @@
 import { useEffect } from 'react'
-import { useQuery, useQueryClient } from '@tanstack/react-query'
+import { useQuery } from '@tanstack/react-query'
 import { queryOptions } from '@tanstack/react-query'
 import { api } from '@/lib/api-client'
 import { usePOSStore } from '@/stores/pos.store'
@@ -21,8 +21,7 @@ function locationsOptions() {
 }
 
 export function POSRegister() {
-  const { locationId, setLocation, currentTransactionId, drawerSessionId, setDrawerSession } = usePOSStore()
-  const queryClient = useQueryClient()
+  const { locationId, setLocation, currentTransactionId, setDrawerSession } = usePOSStore()
 
   // Fetch locations
   const { data: locationsData } = useQuery(locationsOptions())

packages/admin/src/components/pos/pos-top-bar.tsx

@@ -1,6 +1,6 @@
 import { Link, useRouter } from '@tanstack/react-router'
 import { useAuthStore } from '@/stores/auth.store'
-import { usePOSStore } from '@/stores/pos.store'
+
 import { Button } from '@/components/ui/button'
 import { Badge } from '@/components/ui/badge'
 import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@/components/ui/select'