Refactor application structure and initialize core components

I decided to rewrite the program taking into account the experience gained.

internal/ffmpeg/ffprobe.go

@@ -0,0 +1,19 @@
+package ffmpeg
+
+type FFprobeContract interface {
+	SetPath(path string)
+}
+
+type ffprobe struct {
+	path string
+}
+
+func newFFprobe(path string) FFprobeContract {
+	return &ffprobe{
+		path: path,
+	}
+}
+
+func (f *ffprobe) SetPath(path string) {
+	f.path = path
+}