perf: remove slow visitCountriesFor query from device list

- visitCountriesFor queried page_visits (5.5M rows, 1.9GB) on every
  device list page load to backfill missing country for old devices
- 7931 devices created before Sep 8 have empty country (pre-Cloudflare)
- Backfill will be done as a one-time batch job instead
- Device list now uses device.country directly, shows empty if null

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Http/Controllers/Admin/DeviceController.php

@@ -68,10 +68,8 @@ class DeviceController extends Controller
 
         $portal = $this->portal();
         $items = collect($paginator->items());
-        $visitCountries = $this->visitCountriesFor($items);
-        $data = $items->map(function (Device $d) use ($portal, $visitCountries) {
-            $country = CfIpCountry::normalize($d->country)
-                ?? CfIpCountry::normalize($visitCountries[trim((string) $d->ip)] ?? null);
+        $data = $items->map(function (Device $d) use ($portal) {
+            $country = CfIpCountry::normalize($d->country);
 
             return [
                 'id' => $d->id,
@@ -1022,39 +1020,4 @@ class DeviceController extends Controller
             'msg' => '队列顺序已更新',
         ]);
     }
-
-    /**
-     * Latest visit country per IP for devices that have no country of their own.
-     *
-     * @param  Collection<int, Device>  $devices
-     * @return array<string, string>
-     */
-    private function visitCountriesFor(Collection $devices): array
-    {
-        $ips = $devices
-            ->filter(fn (Device $d) => CfIpCountry::normalize($d->country) === null)
-            ->map(fn (Device $d) => trim((string) $d->ip))
-            ->filter()
-            ->unique()
-            ->values();
-        if ($ips->isEmpty()) {
-            return [];
-        }
-
-        $latestIds = PageVisit::query()
-            ->selectRaw('MAX(id) as id')
-            ->whereIn('ip', $ips)
-            ->whereNotNull('country')
-            ->where('country', '!=', '')
-            ->groupBy('ip')
-            ->pluck('id');
-        if ($latestIds->isEmpty()) {
-            return [];
-        }
-
-        return PageVisit::query()
-            ->whereIn('id', $latestIds)
-            ->pluck('country', 'ip')
-            ->all();
-    }
 }