refactor(storage): tighten S3 endpoint URL validation

Reuse the existing SafeWebhookUrl rule on the S3 Storage endpoint field so
the create and edit forms go through the same URL-normalization path as
webhook settings. Adds a matching guard inside S3Storage::testConnection()
so background callers (scheduled backups, database import reuse) also
validate the endpoint before building the S3 client.

Also fixes an IPv6-bracket edge case in SafeWebhookUrl so `http://[::1]`
style hosts are normalized before the filter_var IP check — the rule's
own loopback test was already asserting this behaviour.

app/Livewire/Storage/Create.php

@@ -3,6 +3,7 @@
 namespace App\Livewire\Storage;
 
 use App\Models\S3Storage;
+use App\Rules\SafeWebhookUrl;
 use App\Support\ValidationPatterns;
 use Illuminate\Foundation\Auth\Access\AuthorizesRequests;
 use Illuminate\Support\Uri;
@@ -37,7 +38,7 @@ class Create extends Component
             'key' => 'required|max:255',
             'secret' => 'required|max:255',
             'bucket' => 'required|max:255',
-            'endpoint' => 'required|url|max:255',
+            'endpoint' => ['required', 'max:255', new SafeWebhookUrl],
         ];
     }
 
@@ -55,7 +56,6 @@ class Create extends Component
                 'bucket.required' => 'The Bucket field is required.',
                 'bucket.max' => 'The Bucket may not be greater than 255 characters.',
                 'endpoint.required' => 'The Endpoint field is required.',
-                'endpoint.url' => 'The Endpoint must be a valid URL.',
                 'endpoint.max' => 'The Endpoint may not be greater than 255 characters.',
             ]
         );

app/Livewire/Storage/Form.php

@@ -3,6 +3,7 @@
 namespace App\Livewire\Storage;
 
 use App\Models\S3Storage;
+use App\Rules\SafeWebhookUrl;
 use App\Support\ValidationPatterns;
 use Illuminate\Foundation\Auth\Access\AuthorizesRequests;
 use Illuminate\Support\Facades\DB;
@@ -42,7 +43,7 @@ class Form extends Component
             'key' => 'required|max:255',
             'secret' => 'required|max:255',
             'bucket' => 'required|max:255',
-            'endpoint' => 'required|url|max:255',
+            'endpoint' => ['required', 'max:255', new SafeWebhookUrl],
         ];
     }
 
@@ -60,7 +61,6 @@ class Form extends Component
                 'bucket.required' => 'The Bucket field is required.',
                 'bucket.max' => 'The Bucket may not be greater than 255 characters.',
                 'endpoint.required' => 'The Endpoint field is required.',
-                'endpoint.url' => 'The Endpoint must be a valid URL.',
                 'endpoint.max' => 'The Endpoint may not be greater than 255 characters.',
             ]
         );

app/Models/S3Storage.php

@@ -2,11 +2,13 @@
 
 namespace App\Models;
 
+use App\Rules\SafeWebhookUrl;
 use App\Traits\HasSafeStringAttribute;
 use Illuminate\Database\Eloquent\Casts\Attribute;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Notifications\Messages\MailMessage;
 use Illuminate\Support\Facades\Storage;
+use Illuminate\Support\Facades\Validator;
 
 class S3Storage extends BaseModel
 {
@@ -132,6 +134,14 @@ class S3Storage extends BaseModel
     public function testConnection(bool $shouldSave = false)
     {
         try {
+            $validator = Validator::make(
+                ['endpoint' => $this['endpoint']],
+                ['endpoint' => ['required', new SafeWebhookUrl]],
+            );
+            if ($validator->fails()) {
+                throw new \RuntimeException('S3 endpoint is not allowed: '.$validator->errors()->first('endpoint'));
+            }
+
             $disk = Storage::build([
                 'driver' => 's3',
                 'region' => $this['region'],

app/Rules/SafeWebhookUrl.php

@@ -40,9 +40,15 @@ class SafeWebhookUrl implements ValidationRule
 
         $host = strtolower($host);
 
+        // Strip IPv6 brackets (e.g. "[::1]" -> "::1") before IP checks so bracketed
+        // literals can't sneak past filter_var FILTER_VALIDATE_IP.
+        $hostForIpCheck = (str_starts_with($host, '[') && str_ends_with($host, ']'))
+            ? substr($host, 1, -1)
+            : $host;
+
         // Block well-known dangerous hostnames
         $blockedHosts = ['localhost', '0.0.0.0', '::1'];
-        if (in_array($host, $blockedHosts) || str_ends_with($host, '.internal')) {
+        if (in_array($hostForIpCheck, $blockedHosts) || str_ends_with($host, '.internal')) {
             Log::warning('Webhook URL points to blocked host', [
                 'attribute' => $attribute,
                 'host' => $host,
@@ -55,7 +61,7 @@ class SafeWebhookUrl implements ValidationRule
         }
 
         // Block loopback (127.0.0.0/8) and link-local/metadata (169.254.0.0/16) when IP is provided directly
-        if (filter_var($host, FILTER_VALIDATE_IP) && ($this->isLoopback($host) || $this->isLinkLocal($host))) {
+        if (filter_var($hostForIpCheck, FILTER_VALIDATE_IP) && ($this->isLoopback($hostForIpCheck) || $this->isLinkLocal($hostForIpCheck))) {
             Log::warning('Webhook URL points to blocked IP range', [
                 'attribute' => $attribute,
                 'host' => $host,