Wan 2.1 seamless loop workflow (i2v)

-adding sliders to control the output video fps and interpolation allowing a better speed and fluidity control. adding note on how to use.

-correction of an issue, i've seen after the final interpolation, some frames miss between the last and the first frame, it's invisible with low interpolation but the gap increase with the final interpolation number and can create a jump, it's now good, the output video is perfect seamless.

-the clean vram node was not connected on the 1.1, corrected.

-be carreful, the "save output" button is now turned off by default in the final group to allow user to tune output settings without save every iterations, and the output video framerate is set to 60 fps.

-minors improvements.