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/files/index.tsx

@@ -92,7 +92,7 @@ function FileManagerPage() {
         })
         if (!res.ok) {
           const err = await res.json().catch(() => ({}))
-          toast.error(`Upload failed: ${(err as any).error?.message ?? file.name}`)
+          toast.error(`Upload failed: ${(err as { error?: { message?: string } }).error?.message ?? file.name}`)
         }
       } catch {
         toast.error(`Upload failed: ${file.name}`)