Reverse-geocode a general area label for logged searches

Each search now stores an `area_label` (district/town) reverse-geocoded from its
coarsened ~1km lat/lng bucket via postcodes.io, surfaced in the Filament Searches
admin as a sortable/searchable column plus an area filter. Geocoding is cached 30
days per bucket, queries a 2km radius so low-density buckets still match the
default 100m miss, and fails gracefully to null. Adds `searches:backfill-areas`
(scheduled hourly) to label existing rows and retry stragglers.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/Services/PostcodeService.php

@@ -52,6 +52,77 @@ class PostcodeService
         return $result;
     }
 
+    /**
+     * Reverse-geocode coordinates to a general UK area label (e.g. "Peterborough").
+     *
+     * Coordinates are bucketed to ~1km (2dp) before lookup so the cache is shared
+     * across nearby searches and nothing more precise than the stored bucket is
+     * ever queried. Returns null if the area cannot be determined.
+     */
+    public function reverseResolve(float $lat, float $lng): ?string
+    {
+        $latBucket = round($lat, 2);
+        $lngBucket = round($lng, 2);
+        $cacheKey = "revgeo:{$latBucket},{$lngBucket}";
+
+        $cached = Cache::get($cacheKey);
+
+        if (is_string($cached)) {
+            return $cached;
+        }
+
+        $label = $this->lookupArea($latBucket, $lngBucket);
+
+        if ($label !== null) {
+            Cache::put($cacheKey, $label, self::CACHE_TTL);
+        }
+
+        return $label;
+    }
+
+    private function lookupArea(float $lat, float $lng): ?string
+    {
+        $url = self::BASE_URL.'/postcodes';
+        // radius=2000 (postcodes.io max): we query the ~1km bucket centroid, which
+        // can sit up to ~780m from any real point in the bucket. The default 100m
+        // radius misses in low-density areas, so widen it to guarantee a hit.
+        $logUrl = $url.'?lon='.$lng.'&lat='.$lat.'&radius=2000&limit=1';
+
+        try {
+            $response = $this->apiLogger->send('postcodes_io', 'GET', $logUrl, fn () => Http::timeout(5)
+                ->get($url, ['lon' => $lng, 'lat' => $lat, 'radius' => 2000, 'limit' => 1]));
+
+            if (! $response->successful()) {
+                return null;
+            }
+
+            $results = $response->json('result');
+
+            if (! is_array($results) || ! isset($results[0]) || ! is_array($results[0])) {
+                return null;
+            }
+
+            // Prefer the most human "town/district" field, falling back to broader areas.
+            foreach (['admin_district', 'parish', 'admin_ward', 'region', 'country'] as $field) {
+                $value = $results[0][$field] ?? null;
+
+                if (is_string($value) && $value !== '') {
+                    return $value;
+                }
+            }
+
+            return null;
+        } catch (Throwable $e) {
+            Log::error('PostcodeService: reverse geocode failed', [
+                'lat' => $lat,
+                'lng' => $lng,
+                'error' => $e->getMessage(),
+            ]);
+
+            return null;
+        }
+    }
+
     private function normalisePostcode(string $value): string
     {
         return strtoupper(preg_replace('/\s+/', '', $value));