feat: add danmaku replay player integration

- Add IDanmakuService interface and DanmakuService implementation to parse danmaku XML files
- Add GET /api/record-tasks/{id}/danmaku and GET /api/record-sessions/{id}/danmaku endpoints
- Add DanmakuPlayer Vue component with native video + CSS overlay danmaku rendering
- Add danmakuEngine.ts pure-TypeScript animation loop with binary search, track management, and event notifications
- Add useDanmakuPlayer composable for reusable danmaku data loading
- Integrate danmaku toggle button into RecordTaskDetailView
- Integrate danmaku replay modal dialog into RecordSessionDetailView segment table

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

src/LiveRecorder.Application/Abstractions/Recording/IDanmakuService.cs

@@ -0,0 +1,22 @@
+using LiveRecorder.Application.Models.RecordTasks;
+
+namespace LiveRecorder.Application.Abstractions.Recording;
+
+/// <summary>
+/// Service for reading and parsing danmaku XML files produced by the recording system.
+/// </summary>
+public interface IDanmakuService
+{
+    /// <summary>
+    /// Returns parsed danmaku events for a single recording task (one segment).
+    /// Returns null if the task does not exist or has no danmaku file.
+    /// </summary>
+    Task<DanmakuResponseDto?> GetTaskDanmakuAsync(Guid recordTaskId, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Returns aggregated danmaku events for all tasks in a recording session.
+    /// Returns null if the session does not exist or has no tasks with danmaku.
+    /// Offsets for segments beyond the first are adjusted so they are relative to the session start.
+    /// </summary>
+    Task<SessionDanmakuResponseDto?> GetSessionDanmakuAsync(Guid recordSessionId, CancellationToken cancellationToken = default);
+}

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

@@ -0,0 +1,96 @@
+namespace LiveRecorder.Application.Models.RecordTasks;
+
+/// <summary>
+/// A single parsed danmaku event (chat message or non-chat event like gift/like/member/enter).
+/// </summary>
+public sealed class DanmakuEventDto
+{
+    /// <summary>
+    /// Offset in seconds from the segment's video start time.
+    /// </summary>
+    public double OffsetSeconds { get; init; }
+
+    /// <summary>
+    /// Event type: "chat", "gift", "like", "member", "enter", "superchat", "live", "preparing", or platform-specific types.
+    /// </summary>
+    public required string Type { get; init; }
+
+    /// <summary>
+    /// For chat: the message text. For non-chat events: a descriptive label (e.g., "gift: rose x1").
+    /// </summary>
+    public required string Content { get; init; }
+
+    public string? User { get; init; }
+
+    public string? UserId { get; init; }
+
+    /// <summary>
+    /// Hex color string for chat messages (e.g., "FFFFFF"). Only meaningful for chat events.
+    /// </summary>
+    public string? Color { get; init; }
+
+    /// <summary>
+    /// Font size for chat messages (e.g., 25). Only meaningful for chat events.
+    /// </summary>
+    public int? FontSize { get; init; }
+
+    /// <summary>
+    /// Display mode for chat messages (1 = scroll right-to-left). Only meaningful for chat events.
+    /// </summary>
+    public int? Mode { get; init; }
+
+    /// <summary>
+    /// Unix timestamp in milliseconds when the event occurred (from the platform or recorded time).
+    /// </summary>
+    public long? TimestampMs { get; init; }
+
+    /// <summary>
+    /// For gift events: the gift name (e.g., "rose").
+    /// </summary>
+    public string? GiftName { get; init; }
+
+    /// <summary>
+    /// For gift/like events: the repeat count.
+    /// </summary>
+    public int? Count { get; init; }
+
+    /// <summary>
+    /// Truncated raw payload from the platform (for debugging).
+    /// </summary>
+    public string? Raw { get; init; }
+}
+
+/// <summary>
+/// Danmaku response for a single recording task (one segment).
+/// </summary>
+public sealed class DanmakuResponseDto
+{
+    public Guid RecordTaskId { get; init; }
+
+    public int SegmentIndex { get; init; }
+
+    public string? Platform { get; init; }
+
+    public string? RoomId { get; init; }
+
+    public string? LiveRoomId { get; init; }
+
+    public Guid RecordSessionId { get; init; }
+
+    /// <summary>
+    /// The UTC time when this segment's recording started (anchor for offset calculation).
+    /// </summary>
+    public DateTimeOffset? StartedAt { get; init; }
+
+    public required IReadOnlyList<DanmakuEventDto> Events { get; init; }
+}
+
+/// <summary>
+/// Aggregated danmaku response for an entire recording session (all segments).
+/// </summary>
+public sealed class SessionDanmakuResponseDto
+{
+    public Guid RecordSessionId { get; init; }
+
+    public required IReadOnlyList<DanmakuResponseDto> Tasks { get; init; }
+}