Komica Fix

Fix several Komica issues, including WebP. Fix the following issues on the Komica website: ・Attached images are converted to WebP when downloaded. ・The dark mode toggle does not work. ・Occasionally, none of the attached images on a page display and the [Back to home] link does not work. ・The [Back to board] link contains extra parameters. ・Some board URLs on the mobile homepage are incorrect. The following features are also added: ・When downloading an attached image from its filename link, download the original file instead of a recompressed, smaller file. ・Reminder: If you encounter “Please use the form provided by this board to upload,” add challenges.cloudflare.com to your ad blocker allowlist.