refactor(policies): add uploadBackup ability and enforce it on backup upload endpoint

Introduce a dedicated `uploadBackup` ability on Application, Database,
Service, and ServiceDatabase policies (admin/owner only) and call
`$this->authorize('uploadBackup', $resource)` in `UploadController::upload`
so the backup-upload endpoint goes through the same policy layer as the
rest of the authorization refactor. Adds Pest coverage for each policy
variant plus HTTP-level checks.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/Policies/DatabasePolicy.php

@@ -87,6 +87,24 @@ class DatabasePolicy
         return $teamId !== null && $user->isAdminOfTeam($teamId);
     }
 
+    /**
+     * Determine whether the user can upload a backup archive for this database.
+     */
+    public function uploadBackup(User $user, $database): Response
+    {
+        $teamId = $this->getTeamId($database);
+
+        if ($teamId === null) {
+            return Response::deny('Database team not found.');
+        }
+
+        if ($user->isAdminOfTeam($teamId)) {
+            return Response::allow();
+        }
+
+        return Response::deny('You need at least admin or owner permissions to upload backups for this database.');
+    }
+
     /**
      * Determine whether the user can manage database backups.
      */