[ImgBot] Optimize images

*Total -- 127.20kb -> 97.92kb (23.02%)

/assets/logo.svg -- 1.85kb -> 1.28kb (30.84%)
/assets/logo-dark.svg -- 1.85kb -> 1.28kb (30.68%)
/assets/social-preview.png -- 98.69kb -> 71.90kb (27.15%)
/assets/mark.svg -- 1.04kb -> 0.96kb (7.8%)
/assets/mark-dark.svg -- 1.04kb -> 0.96kb (7.8%)
/assets/social-preview.svg -- 4.04kb -> 3.79kb (6.14%)
/assets/benchmark-agent.svg -- 12.26kb -> 11.59kb (5.42%)
/assets/benchmark-retrieval.svg -- 6.43kb -> 6.15kb (4.33%)

Signed-off-by: ImgBotApp <ImgBotHelp@gmail.com>

Author: ImgBotApp