fix(wopi): stable guest UserId and correct IsAnonymousUser for named guests

Two issues prevented cursor presence from working for named public link guests:

1. Guest UserId was randomly generated on every CheckFileInfo call. The WOPI
   spec requires UserId to be stable per user session. Use a deterministic
   hash of the WOPI token instead so the same guest retains the same identity
   for the duration of the session.

2. IsAnonymousUser was unconditionally set to true for all public link users,
   even when the guest had explicitly entered a display name. Collabora treats
   IsAnonymousUser=true as a privacy signal and hides the cursor from other
   editors. Only set the flag when the guest has no display name (truly
   anonymous), so named guests have visible cursors in collaborative sessions.

Author: Arildm-no

lib/Controller/WopiController.php

@@ -161,7 +161,7 @@ public function checkFileInfo(
 			return new JSONResponse([], Http::STATUS_FORBIDDEN);
 		}
 
-		$guestUserId = 'Guest-' . \OCP\Server::get(\OCP\Security\ISecureRandom::class)->generate(8);
+		$guestUserId = 'Guest-' . substr(hash('sha256', $wopi->getToken()), 0, 16);
 		$user = $this->userManager->get($wopi->getEditorUid());
 		$userDisplayName = $user !== null && !$isPublic ? $user->getDisplayName() : $wopi->getGuestDisplayname();
 		$isSmartPickerEnabled = (bool)$wopi->getCanwrite() && !$isPublic && !$wopi->getDirect();
@@ -293,7 +293,7 @@ public function checkFileInfo(
 
 		if ($isPublic) {
 			$response['UserExtraInfo']['is_guest'] = true; // DEPRECATED
-			$response['IsAnonymousUser'] = true;
+			$response['IsAnonymousUser'] = empty($wopi->getGuestDisplayname());
 		} else {
 			$response['IsAnonymousUser'] = false;
 		}
@@ -485,7 +485,7 @@ public function getSettings(
 			}
 
 			$isPublic = empty($wopi->getEditorUid());
-			$guestUserId = 'Guest-' . \OCP\Server::get(\OCP\Security\ISecureRandom::class)->generate(8);
+			$guestUserId = 'Guest-' . substr(hash('sha256', $wopi->getToken()), 0, 8);
 			$userId = !$isPublic ? $wopi->getEditorUid() : $guestUserId;
 
 			$userConfig = $this->settingsService->generateSettingsConfig($type, $userId);