Generate an SVG as a get-well greeting card illustration. Bold playful cartoon style. Background fill #ECFDF5. Draw a wide rainbow arc (concentric bands in green shades and #34D399) at upper-center. Draw a cartoon sun shape (circle with triangle rays) in #FCD34D at upper area. Draw a simple flower bouquet at lower-center in #34D399 with yellow flower centers. Bold solid fills, uplifting. No text, no labels, no emoji. Output raw SVG code only starting with <svg.

The image shows a vibrant rainbow with a sun in the center, surrounded by lush green leaves and stems. The colors of the rainbow are a mix of green, yellow, and orange, creating a cheerful and inviting atmosphere.