feat: FFmpeg GUI desktop application

Wails v2 + Vue3 + Go project with:
- Encode/Remux/Subtitle burn with hardware acceleration
- Real-time progress with ffmpeg stderr parsing (\r delimiter handling)
- Task queue with cancel support
- Per-task log viewer with color-coded output
- Custom frameless window with resize support
- Dark/light theme toggle
- Hardware encoder detection (NVENC/QSV/AMF)

internal/task/builder.go

@@ -0,0 +1,17 @@
+package task
+
+import "ffmpeg-gui/internal/ffmpeg"
+
+// BuildArgs builds ffmpeg command-line arguments for a task.
+func BuildArgs(t *Task, hwAccel string) []string {
+	switch t.Type {
+	case TypeRemux:
+		return ffmpeg.BuildRemuxArgs(t.InputFile, t.OutputFile, t.Remux, hwAccel)
+	case TypeEncode:
+		return ffmpeg.BuildEncodeArgs(t.InputFile, t.OutputFile, t.Encode, hwAccel)
+	case TypeBurn:
+		return ffmpeg.BuildSubtitleArgs(t.InputFile, t.OutputFile, t.Subtitle, t.Encode, hwAccel)
+	default:
+		return nil
+	}
+}