refactor(media): consolidate upload/edit/download into MediaService

Merge UploadService, EditService, JobOrchestrationService, and
DownloadService into a single MediaService with a unified Job lifecycle
(READY → PROCESSING → SUCCEEDED/FAILED via JobState enum).

- Add MediaController (/api/v1/media) exposing compress, save, and clip
- Add JobController (/api/v1/job) for status polling and file download
- Move clip/thumbnail download into ClipController (/{id}/media, /{id}/thumbnail)
- Move stream saveSection/clip from StreamService into MediaService
- Simplify Job DTO: remove dual ClipOptions/files, add ProgressTracker and download file
- Refactor JobRegistryService.add() → generateJob() to co-locate creation and registration
- Wire FFmpeg out_time_ms progress parsing into StreamActionsService via CommandRunner
- Rename GET /api/v1/auth/user → GET /api/v1/user/me
- Delete DownloadController, MetadataController, UploadController

src/main/java/com/ddf/vodsystem/services/DirectoryService.java

@@ -119,17 +119,6 @@ public class DirectoryService {
         logger.info("Deleted source file: {}", source.getAbsolutePath());
     }
 
-    public String getFileExtension(String filePath) {
-        Path path = Paths.get(filePath);
-        String fileName = path.getFileName().toString();
-
-        int dotIndex = fileName.lastIndexOf('.');
-        if (dotIndex == -1) {
-            return ""; // No extension
-        }
-        return fileName.substring(dotIndex + 1);
-    }
-
     private void createDirectory(String dir) throws IOException {
         // Create the directory if it doesn't exist
         Path outputPath = Paths.get(dir);