fix: 🐛 handle negative lock timeout sentinel from files_lock

When files_lock is configured with the default infinite timeout (-1 min),
the server sends nc:lock-timeout=-60 via PROPFIND. The previous guard only
checked for == 0, causing getLockedUntil() to compute a timestamp 60s in
the past, making the lock appear expired immediately.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: James Manuel <moodyjmz@users.noreply.github.com>

Author: moodyjmz

app/src/main/java/com/nextcloud/ui/fileactions/FileActionsViewModel.kt

@@ -9,6 +9,7 @@ package com.nextcloud.ui.fileactions
 
 import android.os.Bundle
 import androidx.annotation.IdRes
+import androidx.annotation.VisibleForTesting
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.ViewModel
@@ -125,7 +126,8 @@ class FileActionsViewModel @Inject constructor(
         }
     }
 
-    private fun getLockedUntil(file: OCFile): Long? = if (file.lockTimestamp == 0L || file.lockTimeout == 0L) {
+    @VisibleForTesting
+    internal fun getLockedUntil(file: OCFile): Long? = if (file.lockTimestamp == 0L || file.lockTimeout <= 0L) {
         null
     } else {
         (file.lockTimestamp + file.lockTimeout) * TimeConstants.MILLIS_PER_SECOND