Use NAS as primary storage — direct upload when enabled

When NAS storage is enabled, uploaded files go directly to the NAS share
(users/{username}/videos/{title-slug}/) with no permanent local copy kept.
Thumbnails and video are fetched from NAS on demand for streaming/playback.
When NAS is disabled, files are organised into the same directory schema
in local storage.

- VideoController: branch upload flow on NAS enabled/disabled
- NasSyncService: add uploadDirectToNas() for direct NAS writes,
  organizeLocalFiles() for local NAS-schema, localVideoDir() resolver,
  deleteLocalAssets() for post-sync cleanup
- GenerateHlsJob: download from NAS via ensureLocalCopy() when local
  file is absent (NAS-primary mode); clean up temp after HLS generation
- CompressVideoJob: place compressed file alongside original (any dir)
- Video/VideoSlide models: localVideoPath(), localThumbnailPath(),
  thumbnailStorageKey(), localPath(), storageKey() helpers for
  format-agnostic path resolution (old flat paths + new NAS-schema paths)
- MediaController: serve thumbnails from NAS-mirrored paths with NAS fallback
- SuperAdminController: use model path helpers for file deletion
- NasFreeLocalStorage: scan new users/ tree in addition to legacy flat dirs
- Settings: rename "NAS Storage Sync" tab to "NAS Storage", update description

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

app/Jobs/CompressVideoJob.php

@@ -38,9 +38,9 @@ class CompressVideoJob implements ShouldQueue
             return;
         }
 
-        // Create compressed filename
+        // Create compressed file alongside the original
         $compressedFilename = 'compressed_' . $video->filename;
-        $compressedPath = storage_path('app/public/videos/' . $compressedFilename);
+        $compressedPath = dirname($originalPath) . '/' . $compressedFilename;
 
         try {
             $ffmpegConfig = Config::get('ffmpeg');