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/ffmpeg/progress.go

@@ -0,0 +1,85 @@
+package ffmpeg
+
+import (
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// Progress holds real-time encoding progress from ffmpeg stderr.
+type Progress struct {
+	Frame   int64   `json:"frame"`
+	FPS     float64 `json:"fps"`
+	Q       float64 `json:"q"`
+	Size    string  `json:"size"`
+	Time    string  `json:"time"`
+	Bitrate string  `json:"bitrate"`
+	Speed   string  `json:"speed"`
+	Eta     string  `json:"eta"`
+	Percent float64 `json:"percent"`
+}
+
+var progressRe = regexp.MustCompile(
+	`frame=\s*(\d+)\s+fps=\s*([\d.]+)\s+q=\s*([\d.-]+)\s+(?:size=\s*(\S+)\s+)?time=\s*([\d:.]+)\s+bitrate=\s*(\S+)\s+speed=\s*(\S+)`,
+)
+
+func parseProgressLine(line string) (Progress, bool) {
+	m := progressRe.FindStringSubmatch(line)
+	if m == nil {
+		return Progress{}, false
+	}
+
+	frame, _ := strconv.ParseInt(m[1], 10, 64)
+	fps, _ := strconv.ParseFloat(m[2], 64)
+	q, _ := strconv.ParseFloat(m[3], 64)
+
+	return Progress{
+		Frame:   frame,
+		FPS:     fps,
+		Q:       q,
+		Size:    m[4],
+		Time:    m[5],
+		Bitrate: m[6],
+		Speed:   m[7],
+	}, true
+}
+
+// parseSpeedMultiplier converts "1.5x" → 1.5.
+func parseSpeedMultiplier(s string) float64 {
+	s = strings.TrimSuffix(s, "x")
+	v, _ := strconv.ParseFloat(s, 64)
+	return v
+}
+
+// formatSeconds converts seconds to "MM:SS" or "HH:MM:SS".
+func formatSeconds(secs float64) string {
+	if secs < 0 {
+		secs = 0
+	}
+	h := int(secs) / 3600
+	m := (int(secs) % 3600) / 60
+	s := int(secs) % 60
+	if h > 0 {
+		return strconv.Itoa(h) + ":" + pad2(m) + ":" + pad2(s)
+	}
+	return pad2(m) + ":" + pad2(s)
+}
+
+func pad2(n int) string {
+	if n < 10 {
+		return "0" + strconv.Itoa(n)
+	}
+	return strconv.Itoa(n)
+}
+
+// parseTimeSeconds converts "HH:MM:SS.mm" to seconds.
+func parseTimeSeconds(t string) float64 {
+	parts := strings.Split(t, ":")
+	if len(parts) != 3 {
+		return 0
+	}
+	h, _ := strconv.ParseFloat(parts[0], 64)
+	m, _ := strconv.ParseFloat(parts[1], 64)
+	s, _ := strconv.ParseFloat(parts[2], 64)
+	return h*3600 + m*60 + s
+}