feat: batch-delete recording segments whose files are missing

Add a segment-level cleanup alongside the existing session-level one. DeleteMissingFileTasksAsync scans all non-active record tasks, keeps those whose video file no longer exists on disk, and deletes them individually via DeleteTasksAsync (which also drops any session left empty). Exposed as POST /record-tasks/delete-missing-files and a new "清理无文件分片" action in the record tasks view.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/LiveRecorder.Application/Models/RecordTasks/RecordTaskModels.cs

@@ -108,6 +108,11 @@ public sealed class DeleteCompletedRecordTasksRequest
     public bool DeleteFiles { get; set; }
 }
 
+public sealed class DeleteMissingFileRecordTasksRequest
+{
+    public bool DeleteFiles { get; set; }
+}
+
 public sealed class DeleteCompletedRecordTasksResultDto
 {
     public required IReadOnlyList<Guid> DeletedTaskIds { get; init; }

src/LiveRecorder.Application/Services/RecordService.cs

@@ -504,6 +504,32 @@ public sealed class RecordService
         };
     }
 
+    public async Task<DeleteCompletedRecordTasksResultDto> DeleteMissingFileTasksAsync(
+        DeleteMissingFileRecordTasksRequest request,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(request);
+
+        var tasks = await _recordTaskRepository.ListAsync(null, cancellationToken);
+        var missingFileTaskIds = tasks
+            .Where(static task => !IsActiveTaskStatus(task.Status) && !HasExistingVideoFile(task))
+            .Select(static task => task.Id)
+            .ToArray();
+
+        if (missingFileTaskIds.Length == 0)
+        {
+            return CreateEmptyDeleteResult();
+        }
+
+        return await DeleteTasksAsync(
+            new DeleteCompletedRecordTasksRequest
+            {
+                TaskIds = missingFileTaskIds,
+                DeleteFiles = request.DeleteFiles
+            },
+            cancellationToken);
+    }
+
     public async Task<RecordPreviewTicketDto> CreatePreviewTicketAsync(Guid id, string mediaBaseUrl, CancellationToken cancellationToken = default)
     {
         var previewTicket = await _recordMediaService.CreatePreviewTicketAsync(id, cancellationToken);
@@ -823,6 +849,24 @@ public sealed class RecordService
             or RecordTaskStatus.Stopping
             or RecordTaskStatus.Processing;
 
+    private static bool HasExistingVideoFile(RecordTask task)
+    {
+        var candidatePath = !string.IsNullOrWhiteSpace(task.Result?.FilePath)
+            ? task.Result!.FilePath
+            : task.OutputFilePath;
+
+        if (string.IsNullOrWhiteSpace(candidatePath))
+        {
+            return false;
+        }
+
+        var resolvedPath = Path.IsPathRooted(candidatePath)
+            ? candidatePath
+            : Path.GetFullPath(candidatePath, AppContext.BaseDirectory);
+
+        return File.Exists(resolvedPath);
+    }
+
     private static bool IsActiveSessionStatus(RecordSessionStatus status) =>
         status is RecordSessionStatus.Starting or RecordSessionStatus.Running or RecordSessionStatus.Stopping;