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/media/info.go

@@ -0,0 +1,65 @@
+package media
+
+import (
+	"encoding/json"
+	"ffmpeg-gui/internal/ffmpeg"
+	"fmt"
+)
+
+// StreamInfo holds information about a single stream.
+type StreamInfo struct {
+	Index     int    `json:"index"`
+	CodecType string `json:"codec_type"`
+	CodecName string `json:"codec_name"`
+	Width     int    `json:"width,omitempty"`
+	Height    int    `json:"height,omitempty"`
+	Duration  string `json:"duration,omitempty"`
+	BitRate   string `json:"bit_rate,omitempty"`
+	FPS       string `json:"r_frame_rate,omitempty"`
+	Language  string `json:"tags>language,omitempty"`
+}
+
+// FormatInfo holds container format information.
+type FormatInfo struct {
+	Filename string `json:"filename"`
+	Format   string `json:"format_name"`
+	Duration string `json:"duration,omitempty"`
+	Size     string `json:"size,omitempty"`
+	BitRate  string `json:"bit_rate,omitempty"`
+}
+
+// MediaInfo is the top-level ffprobe result.
+type MediaInfo struct {
+	Streams []StreamInfo `json:"streams"`
+	Format  FormatInfo   `json:"format"`
+}
+
+// GetInfo runs ffprobe and returns parsed media information.
+func GetInfo(exec *ffmpeg.Executor, inputFile string) (*MediaInfo, error) {
+	out, err := exec.Probe(
+		"-v", "quiet",
+		"-print_format", "json",
+		"-show_format",
+		"-show_streams",
+		inputFile,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("ffprobe: %w (output: %s)", err, out)
+	}
+
+	var info MediaInfo
+	if err := json.Unmarshal([]byte(out), &info); err != nil {
+		return nil, fmt.Errorf("parse ffprobe json: %w", err)
+	}
+	return &info, nil
+}
+
+// GetDurationSeconds returns the duration in seconds as a float64.
+func (mi *MediaInfo) GetDurationSeconds() float64 {
+	if mi.Format.Duration == "" {
+		return 0
+	}
+	var secs float64
+	fmt.Sscanf(mi.Format.Duration, "%f", &secs)
+	return secs
+}